diff --git a/google/cloud/asset_v1/services/asset_service/async_client.py b/google/cloud/asset_v1/services/asset_service/async_client.py
index e22ca302..aa28e9dd 100644
--- a/google/cloud/asset_v1/services/asset_service/async_client.py
+++ b/google/cloud/asset_v1/services/asset_service/async_client.py
@@ -19,13 +19,15 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-import google.api_core.client_options as ClientOptions  # type: ignore
+from google.api_core.client_options import ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.api_core import operation  # type: ignore
 from google.api_core import operation_async  # type: ignore
 from google.cloud.asset_v1.services.asset_service import pagers
@@ -175,9 +177,9 @@ def __init__(
 
     async def export_assets(
         self,
-        request: asset_service.ExportAssetsRequest = None,
+        request: Union[asset_service.ExportAssetsRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -196,7 +198,7 @@ async def export_assets(
         the export operation usually finishes within 5 minutes.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.ExportAssetsRequest`):
+            request (Union[google.cloud.asset_v1.types.ExportAssetsRequest, dict]):
                 The request object. Export asset request.
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
                 should be retried.
@@ -248,10 +250,10 @@ async def export_assets(
 
     async def list_assets(
         self,
-        request: asset_service.ListAssetsRequest = None,
+        request: Union[asset_service.ListAssetsRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListAssetsAsyncPager:
@@ -259,7 +261,7 @@ async def list_assets(
         paged results in response.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.ListAssetsRequest`):
+            request (Union[google.cloud.asset_v1.types.ListAssetsRequest, dict]):
                 The request object. ListAssets request.
             parent (:class:`str`):
                 Required. Name of the organization or project the assets
@@ -340,9 +342,9 @@ async def list_assets(
 
     async def batch_get_assets_history(
         self,
-        request: asset_service.BatchGetAssetsHistoryRequest = None,
+        request: Union[asset_service.BatchGetAssetsHistoryRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.BatchGetAssetsHistoryResponse:
@@ -355,7 +357,7 @@ async def batch_get_assets_history(
         INVALID_ARGUMENT error.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.BatchGetAssetsHistoryRequest`):
+            request (Union[google.cloud.asset_v1.types.BatchGetAssetsHistoryRequest, dict]):
                 The request object. Batch get assets history request.
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
                 should be retried.
@@ -402,10 +404,10 @@ async def batch_get_assets_history(
 
     async def create_feed(
         self,
-        request: asset_service.CreateFeedRequest = None,
+        request: Union[asset_service.CreateFeedRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -414,7 +416,7 @@ async def create_feed(
         updates.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.CreateFeedRequest`):
+            request (Union[google.cloud.asset_v1.types.CreateFeedRequest, dict]):
                 The request object. Create asset feed request.
             parent (:class:`str`):
                 Required. The name of the
@@ -486,17 +488,17 @@ async def create_feed(
 
     async def get_feed(
         self,
-        request: asset_service.GetFeedRequest = None,
+        request: Union[asset_service.GetFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
         r"""Gets details about an asset feed.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.GetFeedRequest`):
+            request (Union[google.cloud.asset_v1.types.GetFeedRequest, dict]):
                 The request object. Get asset feed request.
             name (:class:`str`):
                 Required. The name of the Feed and it must be in the
@@ -573,10 +575,10 @@ async def get_feed(
 
     async def list_feeds(
         self,
-        request: asset_service.ListFeedsRequest = None,
+        request: Union[asset_service.ListFeedsRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.ListFeedsResponse:
@@ -584,7 +586,7 @@ async def list_feeds(
         project/folder/organization.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.ListFeedsRequest`):
+            request (Union[google.cloud.asset_v1.types.ListFeedsRequest, dict]):
                 The request object. List asset feeds request.
             parent (:class:`str`):
                 Required. The parent
@@ -656,17 +658,17 @@ async def list_feeds(
 
     async def update_feed(
         self,
-        request: asset_service.UpdateFeedRequest = None,
+        request: Union[asset_service.UpdateFeedRequest, dict] = None,
         *,
         feed: asset_service.Feed = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
         r"""Updates an asset feed configuration.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.UpdateFeedRequest`):
+            request (Union[google.cloud.asset_v1.types.UpdateFeedRequest, dict]):
                 The request object. Update asset feed request.
             feed (:class:`google.cloud.asset_v1.types.Feed`):
                 Required. The new values of feed details. It must match
@@ -736,17 +738,17 @@ async def update_feed(
 
     async def delete_feed(
         self,
-        request: asset_service.DeleteFeedRequest = None,
+        request: Union[asset_service.DeleteFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> None:
         r"""Deletes an asset feed.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.DeleteFeedRequest`):
+            request (Union[google.cloud.asset_v1.types.DeleteFeedRequest, dict]):
                 The request object.
             name (:class:`str`):
                 Required. The name of the feed and it must be in the
@@ -811,12 +813,12 @@ async def delete_feed(
 
     async def search_all_resources(
         self,
-        request: asset_service.SearchAllResourcesRequest = None,
+        request: Union[asset_service.SearchAllResourcesRequest, dict] = None,
         *,
         scope: str = None,
         query: str = None,
         asset_types: Sequence[str] = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllResourcesAsyncPager:
@@ -826,7 +828,7 @@ async def search_all_resources(
         desired scope, otherwise the request will be rejected.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.SearchAllResourcesRequest`):
+            request (Union[google.cloud.asset_v1.types.SearchAllResourcesRequest, dict]):
                 The request object. Search all resources request.
             scope (:class:`str`):
                 Required. A scope can be a project, a folder, or an
@@ -993,11 +995,11 @@ async def search_all_resources(
 
     async def search_all_iam_policies(
         self,
-        request: asset_service.SearchAllIamPoliciesRequest = None,
+        request: Union[asset_service.SearchAllIamPoliciesRequest, dict] = None,
         *,
         scope: str = None,
         query: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllIamPoliciesAsyncPager:
@@ -1007,7 +1009,7 @@ async def search_all_iam_policies(
         desired scope, otherwise the request will be rejected.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.SearchAllIamPoliciesRequest`):
+            request (Union[google.cloud.asset_v1.types.SearchAllIamPoliciesRequest, dict]):
                 The request object. Search all IAM policies request.
             scope (:class:`str`):
                 Required. A scope can be a project, a folder, or an
@@ -1154,9 +1156,9 @@ async def search_all_iam_policies(
 
     async def analyze_iam_policy(
         self,
-        request: asset_service.AnalyzeIamPolicyRequest = None,
+        request: Union[asset_service.AnalyzeIamPolicyRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.AnalyzeIamPolicyResponse:
@@ -1164,7 +1166,7 @@ async def analyze_iam_policy(
         what accesses on which resources.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.AnalyzeIamPolicyRequest`):
+            request (Union[google.cloud.asset_v1.types.AnalyzeIamPolicyRequest, dict]):
                 The request object. A request message for
                 [AssetService.AnalyzeIamPolicy][google.cloud.asset.v1.AssetService.AnalyzeIamPolicy].
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
@@ -1215,9 +1217,9 @@ async def analyze_iam_policy(
 
     async def analyze_iam_policy_longrunning(
         self,
-        request: asset_service.AnalyzeIamPolicyLongrunningRequest = None,
+        request: Union[asset_service.AnalyzeIamPolicyLongrunningRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -1235,7 +1237,7 @@ async def analyze_iam_policy_longrunning(
         for the long-running operation.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.AnalyzeIamPolicyLongrunningRequest`):
+            request (Union[google.cloud.asset_v1.types.AnalyzeIamPolicyLongrunningRequest, dict]):
                 The request object. A request message for
                 [AssetService.AnalyzeIamPolicyLongrunning][google.cloud.asset.v1.AssetService.AnalyzeIamPolicyLongrunning].
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
@@ -1289,9 +1291,9 @@ async def analyze_iam_policy_longrunning(
 
     async def analyze_move(
         self,
-        request: asset_service.AnalyzeMoveRequest = None,
+        request: Union[asset_service.AnalyzeMoveRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.AnalyzeMoveResponse:
@@ -1304,7 +1306,7 @@ async def analyze_move(
         takes place.
 
         Args:
-            request (:class:`google.cloud.asset_v1.types.AnalyzeMoveRequest`):
+            request (Union[google.cloud.asset_v1.types.AnalyzeMoveRequest, dict]):
                 The request object. The request message for performing
                 resource move analysis.
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
diff --git a/google/cloud/asset_v1/services/asset_service/client.py b/google/cloud/asset_v1/services/asset_service/client.py
index 8e5e62fb..7938ab49 100644
--- a/google/cloud/asset_v1/services/asset_service/client.py
+++ b/google/cloud/asset_v1/services/asset_service/client.py
@@ -30,6 +30,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.api_core import operation  # type: ignore
 from google.api_core import operation_async  # type: ignore
 from google.cloud.asset_v1.services.asset_service import pagers
@@ -412,7 +414,7 @@ def export_assets(
         self,
         request: Union[asset_service.ExportAssetsRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -487,7 +489,7 @@ def list_assets(
         request: Union[asset_service.ListAssetsRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListAssetsPager:
@@ -568,7 +570,7 @@ def batch_get_assets_history(
         self,
         request: Union[asset_service.BatchGetAssetsHistoryRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.BatchGetAssetsHistoryResponse:
@@ -622,7 +624,7 @@ def create_feed(
         request: Union[asset_service.CreateFeedRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -706,7 +708,7 @@ def get_feed(
         request: Union[asset_service.GetFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -783,7 +785,7 @@ def list_feeds(
         request: Union[asset_service.ListFeedsRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.ListFeedsResponse:
@@ -856,7 +858,7 @@ def update_feed(
         request: Union[asset_service.UpdateFeedRequest, dict] = None,
         *,
         feed: asset_service.Feed = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -936,7 +938,7 @@ def delete_feed(
         request: Union[asset_service.DeleteFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> None:
@@ -1003,7 +1005,7 @@ def search_all_resources(
         scope: str = None,
         query: str = None,
         asset_types: Sequence[str] = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllResourcesPager:
@@ -1175,7 +1177,7 @@ def search_all_iam_policies(
         *,
         scope: str = None,
         query: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllIamPoliciesPager:
@@ -1325,7 +1327,7 @@ def analyze_iam_policy(
         self,
         request: Union[asset_service.AnalyzeIamPolicyRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.AnalyzeIamPolicyResponse:
@@ -1378,7 +1380,7 @@ def analyze_iam_policy_longrunning(
         self,
         request: Union[asset_service.AnalyzeIamPolicyLongrunningRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
@@ -1455,7 +1457,7 @@ def analyze_move(
         self,
         request: Union[asset_service.AnalyzeMoveRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.AnalyzeMoveResponse:
diff --git a/google/cloud/asset_v1/services/asset_service/transports/base.py b/google/cloud/asset_v1/services/asset_service/transports/base.py
index 00490870..004ef6b7 100644
--- a/google/cloud/asset_v1/services/asset_service/transports/base.py
+++ b/google/cloud/asset_v1/services/asset_service/transports/base.py
@@ -15,7 +15,6 @@
 #
 import abc
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Union
-import packaging.version
 import pkg_resources
 
 import google.auth  # type: ignore
@@ -38,15 +37,6 @@
 except pkg_resources.DistributionNotFound:
     DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo()
 
-try:
-    # google.auth.__version__ was added in 1.26.0
-    _GOOGLE_AUTH_VERSION = google.auth.__version__
-except AttributeError:
-    try:  # try pkg_resources if it is available
-        _GOOGLE_AUTH_VERSION = pkg_resources.get_distribution("google-auth").version
-    except pkg_resources.DistributionNotFound:  # pragma: NO COVER
-        _GOOGLE_AUTH_VERSION = None
-
 
 class AssetServiceTransport(abc.ABC):
     """Abstract transport class for AssetService."""
@@ -96,7 +86,7 @@ def __init__(
             host += ":443"
         self._host = host
 
-        scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
+        scopes_kwargs = {"scopes": scopes, "default_scopes": self.AUTH_SCOPES}
 
         # Save the scopes.
         self._scopes = scopes
@@ -129,29 +119,6 @@ def __init__(
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): This method is in the base transport
-    # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-auth is increased.
-
-    # TODO: Remove this function once google-auth >= 1.25.0 is required
-    @classmethod
-    def _get_scopes_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Optional[Sequence[str]]]:
-        """Returns scopes kwargs to pass to google-auth methods depending on the google-auth version"""
-
-        scopes_kwargs = {}
-
-        if _GOOGLE_AUTH_VERSION and (
-            packaging.version.parse(_GOOGLE_AUTH_VERSION)
-            >= packaging.version.parse("1.25.0")
-        ):
-            scopes_kwargs = {"scopes": scopes, "default_scopes": cls.AUTH_SCOPES}
-        else:
-            scopes_kwargs = {"scopes": scopes or cls.AUTH_SCOPES}
-
-        return scopes_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
@@ -301,7 +268,7 @@ def close(self):
         raise NotImplementedError()
 
     @property
-    def operations_client(self) -> operations_v1.OperationsClient:
+    def operations_client(self):
         """Return the client designed to process long-running operations."""
         raise NotImplementedError()
 
diff --git a/google/cloud/asset_v1/services/asset_service/transports/grpc.py b/google/cloud/asset_v1/services/asset_service/transports/grpc.py
index ea1e6748..6be0a437 100644
--- a/google/cloud/asset_v1/services/asset_service/transports/grpc.py
+++ b/google/cloud/asset_v1/services/asset_service/transports/grpc.py
@@ -113,7 +113,7 @@ def __init__(
         self._grpc_channel = None
         self._ssl_channel_credentials = ssl_channel_credentials
         self._stubs: Dict[str, Callable] = {}
-        self._operations_client = None
+        self._operations_client: Optional[operations_v1.OperationsClient] = None
 
         if api_mtls_endpoint:
             warnings.warn("api_mtls_endpoint is deprecated", DeprecationWarning)
diff --git a/google/cloud/asset_v1/services/asset_service/transports/grpc_asyncio.py b/google/cloud/asset_v1/services/asset_service/transports/grpc_asyncio.py
index 5453cfb0..173bb97d 100644
--- a/google/cloud/asset_v1/services/asset_service/transports/grpc_asyncio.py
+++ b/google/cloud/asset_v1/services/asset_service/transports/grpc_asyncio.py
@@ -21,7 +21,6 @@
 from google.api_core import operations_v1  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
-import packaging.version
 
 import grpc  # type: ignore
 from grpc.experimental import aio  # type: ignore
@@ -160,7 +159,7 @@ def __init__(
         self._grpc_channel = None
         self._ssl_channel_credentials = ssl_channel_credentials
         self._stubs: Dict[str, Callable] = {}
-        self._operations_client = None
+        self._operations_client: Optional[operations_v1.OperationsAsyncClient] = None
 
         if api_mtls_endpoint:
             warnings.warn("api_mtls_endpoint is deprecated", DeprecationWarning)
diff --git a/google/cloud/asset_v1/types/asset_service.py b/google/cloud/asset_v1/types/asset_service.py
index dc2e0068..0a20700c 100644
--- a/google/cloud/asset_v1/types/asset_service.py
+++ b/google/cloud/asset_v1/types/asset_service.py
@@ -483,13 +483,22 @@ class DeleteFeedRequest(proto.Message):
 class OutputConfig(proto.Message):
     r"""Output configuration for export assets destination.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         gcs_destination (google.cloud.asset_v1.types.GcsDestination):
             Destination on Cloud Storage.
+            This field is a member of `oneof`_ ``destination``.
         bigquery_destination (google.cloud.asset_v1.types.BigQueryDestination):
             Destination on BigQuery. The output table
             stores the fields in asset proto as columns in
             BigQuery.
+            This field is a member of `oneof`_ ``destination``.
     """
 
     gcs_destination = proto.Field(
@@ -503,9 +512,12 @@ class OutputConfig(proto.Message):
 class OutputResult(proto.Message):
     r"""Output result of export assets.
 
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         gcs_result (google.cloud.asset_v1.types.GcsOutputResult):
             Export result on Cloud Storage.
+            This field is a member of `oneof`_ ``result``.
     """
 
     gcs_result = proto.Field(
@@ -528,6 +540,13 @@ class GcsOutputResult(proto.Message):
 class GcsDestination(proto.Message):
     r"""A Cloud Storage location.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         uri (str):
             The uri of the Cloud Storage object. It's the same uri that
@@ -540,6 +559,7 @@ class GcsDestination(proto.Message):
             there is no
             `hold <https://cloud.google.com/storage/docs/object-holds>`__,
             it will be overwritten with the exported result.
+            This field is a member of `oneof`_ ``object_uri``.
         uri_prefix (str):
             The uri prefix of all generated Cloud Storage objects.
             Example: "gs://bucket_name/object_name_prefix". Each object
@@ -550,6 +570,7 @@ class GcsDestination(proto.Message):
             compute.googleapis.com/Disk assets. An INVALID_ARGUMENT
             error will be returned if file with the same name
             "gs://bucket_name/object_name_prefix" already exists.
+            This field is a member of `oneof`_ ``object_uri``.
     """
 
     uri = proto.Field(proto.STRING, number=1, oneof="object_uri",)
@@ -680,9 +701,12 @@ class PubsubDestination(proto.Message):
 class FeedOutputConfig(proto.Message):
     r"""Output configuration for asset feed destination.
 
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         pubsub_destination (google.cloud.asset_v1.types.PubsubDestination):
             Destination on Pub/Sub.
+            This field is a member of `oneof`_ ``destination``.
     """
 
     pubsub_destination = proto.Field(
@@ -1304,12 +1328,15 @@ class Options(proto.Message):
     class ConditionContext(proto.Message):
         r"""The IAM conditions context.
 
+        .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
         Attributes:
             access_time (google.protobuf.timestamp_pb2.Timestamp):
                 The hypothetical access timestamp to evaluate IAM
                 conditions. Note that this value must not be earlier than
                 the current time; otherwise, an INVALID_ARGUMENT error will
                 be returned.
+                This field is a member of `oneof`_ ``TimeContext``.
         """
 
         access_time = proto.Field(
@@ -1419,11 +1446,20 @@ class IamPolicyAnalysisOutputConfig(proto.Message):
     r"""Output configuration for export IAM policy analysis
     destination.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         gcs_destination (google.cloud.asset_v1.types.IamPolicyAnalysisOutputConfig.GcsDestination):
             Destination on Cloud Storage.
+            This field is a member of `oneof`_ ``destination``.
         bigquery_destination (google.cloud.asset_v1.types.IamPolicyAnalysisOutputConfig.BigQueryDestination):
             Destination on BigQuery.
+            This field is a member of `oneof`_ ``destination``.
     """
 
     class GcsDestination(proto.Message):
@@ -1598,6 +1634,13 @@ class AnalyzeMoveResponse(proto.Message):
 class MoveAnalysis(proto.Message):
     r"""A message to group the analysis information.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         display_name (str):
             The user friendly display name of the
@@ -1605,9 +1648,11 @@ class MoveAnalysis(proto.Message):
         analysis (google.cloud.asset_v1.types.MoveAnalysisResult):
             Analysis result of moving the target
             resource.
+            This field is a member of `oneof`_ ``result``.
         error (google.rpc.status_pb2.Status):
             Description of error encountered when
             performing the analysis.
+            This field is a member of `oneof`_ ``result``.
     """
 
     display_name = proto.Field(proto.STRING, number=1,)
diff --git a/google/cloud/asset_v1/types/assets.py b/google/cloud/asset_v1/types/assets.py
index 8c2d81a0..bf4e868d 100644
--- a/google/cloud/asset_v1/types/assets.py
+++ b/google/cloud/asset_v1/types/assets.py
@@ -112,6 +112,13 @@ class Asset(proto.Message):
     types <https://cloud.google.com/asset-inventory/docs/supported-asset-types>`__
     for more information.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         update_time (google.protobuf.timestamp_pb2.Timestamp):
             The last update timestamp of an asset. update_time is
@@ -152,12 +159,15 @@ class Asset(proto.Message):
         access_policy (google.identity.accesscontextmanager.v1.access_policy_pb2.AccessPolicy):
             Please also refer to the `access policy user
             guide <https://cloud.google.com/access-context-manager/docs/overview#access-policies>`__.
+            This field is a member of `oneof`_ ``access_context_policy``.
         access_level (google.identity.accesscontextmanager.v1.access_level_pb2.AccessLevel):
             Please also refer to the `access level user
             guide <https://cloud.google.com/access-context-manager/docs/overview#access-levels>`__.
+            This field is a member of `oneof`_ ``access_context_policy``.
         service_perimeter (google.identity.accesscontextmanager.v1.service_perimeter_pb2.ServicePerimeter):
             Please also refer to the `service perimeter user
             guide <https://cloud.google.com/vpc-service-controls/docs/overview>`__.
+            This field is a member of `oneof`_ ``access_context_policy``.
         os_inventory (google.cloud.osconfig_v1.Inventory):
             A representation of runtime OS Inventory information. See
             `this
@@ -937,11 +947,20 @@ class Resource(proto.Message):
     class Access(proto.Message):
         r"""An IAM role or permission under analysis.
 
+        This message has `oneof`_ fields (mutually exclusive fields).
+        For each oneof, at most one member field can be set at the same time.
+        Setting any member of the oneof automatically clears all other
+        members.
+
+        .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
         Attributes:
             role (str):
                 The role.
+                This field is a member of `oneof`_ ``oneof_access``.
             permission (str):
                 The permission.
+                This field is a member of `oneof`_ ``oneof_access``.
             analysis_state (google.cloud.asset_v1.types.IamPolicyAnalysisState):
                 The analysis state of this access.
         """
diff --git a/google/cloud/asset_v1p1beta1/services/asset_service/async_client.py b/google/cloud/asset_v1p1beta1/services/asset_service/async_client.py
index 5a6fa9ce..98dd7848 100644
--- a/google/cloud/asset_v1p1beta1/services/asset_service/async_client.py
+++ b/google/cloud/asset_v1p1beta1/services/asset_service/async_client.py
@@ -19,13 +19,15 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-import google.api_core.client_options as ClientOptions  # type: ignore
+from google.api_core.client_options import ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.asset_v1p1beta1.services.asset_service import pagers
 from google.cloud.asset_v1p1beta1.types import asset_service
 from google.cloud.asset_v1p1beta1.types import assets
@@ -158,12 +160,12 @@ def __init__(
 
     async def search_all_resources(
         self,
-        request: asset_service.SearchAllResourcesRequest = None,
+        request: Union[asset_service.SearchAllResourcesRequest, dict] = None,
         *,
         scope: str = None,
         query: str = None,
         asset_types: Sequence[str] = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllResourcesAsyncPager:
@@ -176,7 +178,7 @@ async def search_all_resources(
         requested scope, otherwise it will be rejected.
 
         Args:
-            request (:class:`google.cloud.asset_v1p1beta1.types.SearchAllResourcesRequest`):
+            request (Union[google.cloud.asset_v1p1beta1.types.SearchAllResourcesRequest, dict]):
                 The request object. Search all resources request.
             scope (:class:`str`):
                 Required. The relative name of an asset. The search is
@@ -278,11 +280,11 @@ async def search_all_resources(
 
     async def search_all_iam_policies(
         self,
-        request: asset_service.SearchAllIamPoliciesRequest = None,
+        request: Union[asset_service.SearchAllIamPoliciesRequest, dict] = None,
         *,
         scope: str = None,
         query: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllIamPoliciesAsyncPager:
@@ -296,7 +298,7 @@ async def search_all_iam_policies(
         requested scope, otherwise it will be rejected.
 
         Args:
-            request (:class:`google.cloud.asset_v1p1beta1.types.SearchAllIamPoliciesRequest`):
+            request (Union[google.cloud.asset_v1p1beta1.types.SearchAllIamPoliciesRequest, dict]):
                 The request object. Search all IAM policies request.
             scope (:class:`str`):
                 Required. The relative name of an asset. The search is
diff --git a/google/cloud/asset_v1p1beta1/services/asset_service/client.py b/google/cloud/asset_v1p1beta1/services/asset_service/client.py
index 35215ae9..9778d40a 100644
--- a/google/cloud/asset_v1p1beta1/services/asset_service/client.py
+++ b/google/cloud/asset_v1p1beta1/services/asset_service/client.py
@@ -30,6 +30,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.asset_v1p1beta1.services.asset_service import pagers
 from google.cloud.asset_v1p1beta1.types import asset_service
 from google.cloud.asset_v1p1beta1.types import assets
@@ -337,7 +339,7 @@ def search_all_resources(
         scope: str = None,
         query: str = None,
         asset_types: Sequence[str] = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllResourcesPager:
@@ -446,7 +448,7 @@ def search_all_iam_policies(
         *,
         scope: str = None,
         query: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.SearchAllIamPoliciesPager:
diff --git a/google/cloud/asset_v1p1beta1/services/asset_service/transports/base.py b/google/cloud/asset_v1p1beta1/services/asset_service/transports/base.py
index b4403329..21bcf429 100644
--- a/google/cloud/asset_v1p1beta1/services/asset_service/transports/base.py
+++ b/google/cloud/asset_v1p1beta1/services/asset_service/transports/base.py
@@ -15,7 +15,6 @@
 #
 import abc
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Union
-import packaging.version
 import pkg_resources
 
 import google.auth  # type: ignore
@@ -35,15 +34,6 @@
 except pkg_resources.DistributionNotFound:
     DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo()
 
-try:
-    # google.auth.__version__ was added in 1.26.0
-    _GOOGLE_AUTH_VERSION = google.auth.__version__
-except AttributeError:
-    try:  # try pkg_resources if it is available
-        _GOOGLE_AUTH_VERSION = pkg_resources.get_distribution("google-auth").version
-    except pkg_resources.DistributionNotFound:  # pragma: NO COVER
-        _GOOGLE_AUTH_VERSION = None
-
 
 class AssetServiceTransport(abc.ABC):
     """Abstract transport class for AssetService."""
@@ -93,7 +83,7 @@ def __init__(
             host += ":443"
         self._host = host
 
-        scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
+        scopes_kwargs = {"scopes": scopes, "default_scopes": self.AUTH_SCOPES}
 
         # Save the scopes.
         self._scopes = scopes
@@ -126,29 +116,6 @@ def __init__(
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): This method is in the base transport
-    # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-auth is increased.
-
-    # TODO: Remove this function once google-auth >= 1.25.0 is required
-    @classmethod
-    def _get_scopes_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Optional[Sequence[str]]]:
-        """Returns scopes kwargs to pass to google-auth methods depending on the google-auth version"""
-
-        scopes_kwargs = {}
-
-        if _GOOGLE_AUTH_VERSION and (
-            packaging.version.parse(_GOOGLE_AUTH_VERSION)
-            >= packaging.version.parse("1.25.0")
-        ):
-            scopes_kwargs = {"scopes": scopes, "default_scopes": cls.AUTH_SCOPES}
-        else:
-            scopes_kwargs = {"scopes": scopes or cls.AUTH_SCOPES}
-
-        return scopes_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
diff --git a/google/cloud/asset_v1p1beta1/services/asset_service/transports/grpc_asyncio.py b/google/cloud/asset_v1p1beta1/services/asset_service/transports/grpc_asyncio.py
index f418c80f..62c7b9f6 100644
--- a/google/cloud/asset_v1p1beta1/services/asset_service/transports/grpc_asyncio.py
+++ b/google/cloud/asset_v1p1beta1/services/asset_service/transports/grpc_asyncio.py
@@ -20,7 +20,6 @@
 from google.api_core import grpc_helpers_async  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
-import packaging.version
 
 import grpc  # type: ignore
 from grpc.experimental import aio  # type: ignore
diff --git a/google/cloud/asset_v1p2beta1/services/asset_service/async_client.py b/google/cloud/asset_v1p2beta1/services/asset_service/async_client.py
index a35725e4..5fc78da3 100644
--- a/google/cloud/asset_v1p2beta1/services/asset_service/async_client.py
+++ b/google/cloud/asset_v1p2beta1/services/asset_service/async_client.py
@@ -19,13 +19,15 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-import google.api_core.client_options as ClientOptions  # type: ignore
+from google.api_core.client_options import ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.asset_v1p2beta1.types import asset_service
 from .transports.base import AssetServiceTransport, DEFAULT_CLIENT_INFO
 from .transports.grpc_asyncio import AssetServiceGrpcAsyncIOTransport
@@ -158,10 +160,10 @@ def __init__(
 
     async def create_feed(
         self,
-        request: asset_service.CreateFeedRequest = None,
+        request: Union[asset_service.CreateFeedRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -170,7 +172,7 @@ async def create_feed(
         updates.
 
         Args:
-            request (:class:`google.cloud.asset_v1p2beta1.types.CreateFeedRequest`):
+            request (Union[google.cloud.asset_v1p2beta1.types.CreateFeedRequest, dict]):
                 The request object. Create asset feed request.
             parent (:class:`str`):
                 Required. The name of the
@@ -242,17 +244,17 @@ async def create_feed(
 
     async def get_feed(
         self,
-        request: asset_service.GetFeedRequest = None,
+        request: Union[asset_service.GetFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
         r"""Gets details about an asset feed.
 
         Args:
-            request (:class:`google.cloud.asset_v1p2beta1.types.GetFeedRequest`):
+            request (Union[google.cloud.asset_v1p2beta1.types.GetFeedRequest, dict]):
                 The request object. Get asset feed request.
             name (:class:`str`):
                 Required. The name of the Feed and it must be in the
@@ -329,10 +331,10 @@ async def get_feed(
 
     async def list_feeds(
         self,
-        request: asset_service.ListFeedsRequest = None,
+        request: Union[asset_service.ListFeedsRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.ListFeedsResponse:
@@ -340,7 +342,7 @@ async def list_feeds(
         project/folder/organization.
 
         Args:
-            request (:class:`google.cloud.asset_v1p2beta1.types.ListFeedsRequest`):
+            request (Union[google.cloud.asset_v1p2beta1.types.ListFeedsRequest, dict]):
                 The request object. List asset feeds request.
             parent (:class:`str`):
                 Required. The parent
@@ -412,17 +414,17 @@ async def list_feeds(
 
     async def update_feed(
         self,
-        request: asset_service.UpdateFeedRequest = None,
+        request: Union[asset_service.UpdateFeedRequest, dict] = None,
         *,
         feed: asset_service.Feed = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
         r"""Updates an asset feed configuration.
 
         Args:
-            request (:class:`google.cloud.asset_v1p2beta1.types.UpdateFeedRequest`):
+            request (Union[google.cloud.asset_v1p2beta1.types.UpdateFeedRequest, dict]):
                 The request object. Update asset feed request.
             feed (:class:`google.cloud.asset_v1p2beta1.types.Feed`):
                 Required. The new values of feed details. It must match
@@ -492,17 +494,17 @@ async def update_feed(
 
     async def delete_feed(
         self,
-        request: asset_service.DeleteFeedRequest = None,
+        request: Union[asset_service.DeleteFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> None:
         r"""Deletes an asset feed.
 
         Args:
-            request (:class:`google.cloud.asset_v1p2beta1.types.DeleteFeedRequest`):
+            request (Union[google.cloud.asset_v1p2beta1.types.DeleteFeedRequest, dict]):
                 The request object.
             name (:class:`str`):
                 Required. The name of the feed and it must be in the
diff --git a/google/cloud/asset_v1p2beta1/services/asset_service/client.py b/google/cloud/asset_v1p2beta1/services/asset_service/client.py
index 68b744d7..b2174f2b 100644
--- a/google/cloud/asset_v1p2beta1/services/asset_service/client.py
+++ b/google/cloud/asset_v1p2beta1/services/asset_service/client.py
@@ -30,6 +30,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.asset_v1p2beta1.types import asset_service
 from .transports.base import AssetServiceTransport, DEFAULT_CLIENT_INFO
 from .transports.grpc import AssetServiceGrpcTransport
@@ -344,7 +346,7 @@ def create_feed(
         request: Union[asset_service.CreateFeedRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -428,7 +430,7 @@ def get_feed(
         request: Union[asset_service.GetFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -505,7 +507,7 @@ def list_feeds(
         request: Union[asset_service.ListFeedsRequest, dict] = None,
         *,
         parent: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.ListFeedsResponse:
@@ -578,7 +580,7 @@ def update_feed(
         request: Union[asset_service.UpdateFeedRequest, dict] = None,
         *,
         feed: asset_service.Feed = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.Feed:
@@ -658,7 +660,7 @@ def delete_feed(
         request: Union[asset_service.DeleteFeedRequest, dict] = None,
         *,
         name: str = None,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> None:
diff --git a/google/cloud/asset_v1p2beta1/services/asset_service/transports/base.py b/google/cloud/asset_v1p2beta1/services/asset_service/transports/base.py
index 4aadbd52..2d9ec603 100644
--- a/google/cloud/asset_v1p2beta1/services/asset_service/transports/base.py
+++ b/google/cloud/asset_v1p2beta1/services/asset_service/transports/base.py
@@ -15,7 +15,6 @@
 #
 import abc
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Union
-import packaging.version
 import pkg_resources
 
 import google.auth  # type: ignore
@@ -36,15 +35,6 @@
 except pkg_resources.DistributionNotFound:
     DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo()
 
-try:
-    # google.auth.__version__ was added in 1.26.0
-    _GOOGLE_AUTH_VERSION = google.auth.__version__
-except AttributeError:
-    try:  # try pkg_resources if it is available
-        _GOOGLE_AUTH_VERSION = pkg_resources.get_distribution("google-auth").version
-    except pkg_resources.DistributionNotFound:  # pragma: NO COVER
-        _GOOGLE_AUTH_VERSION = None
-
 
 class AssetServiceTransport(abc.ABC):
     """Abstract transport class for AssetService."""
@@ -94,7 +84,7 @@ def __init__(
             host += ":443"
         self._host = host
 
-        scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
+        scopes_kwargs = {"scopes": scopes, "default_scopes": self.AUTH_SCOPES}
 
         # Save the scopes.
         self._scopes = scopes
@@ -127,29 +117,6 @@ def __init__(
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): This method is in the base transport
-    # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-auth is increased.
-
-    # TODO: Remove this function once google-auth >= 1.25.0 is required
-    @classmethod
-    def _get_scopes_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Optional[Sequence[str]]]:
-        """Returns scopes kwargs to pass to google-auth methods depending on the google-auth version"""
-
-        scopes_kwargs = {}
-
-        if _GOOGLE_AUTH_VERSION and (
-            packaging.version.parse(_GOOGLE_AUTH_VERSION)
-            >= packaging.version.parse("1.25.0")
-        ):
-            scopes_kwargs = {"scopes": scopes, "default_scopes": cls.AUTH_SCOPES}
-        else:
-            scopes_kwargs = {"scopes": scopes or cls.AUTH_SCOPES}
-
-        return scopes_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
diff --git a/google/cloud/asset_v1p2beta1/services/asset_service/transports/grpc_asyncio.py b/google/cloud/asset_v1p2beta1/services/asset_service/transports/grpc_asyncio.py
index 1e264ea0..8e9b18f9 100644
--- a/google/cloud/asset_v1p2beta1/services/asset_service/transports/grpc_asyncio.py
+++ b/google/cloud/asset_v1p2beta1/services/asset_service/transports/grpc_asyncio.py
@@ -20,7 +20,6 @@
 from google.api_core import grpc_helpers_async  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
-import packaging.version
 
 import grpc  # type: ignore
 from grpc.experimental import aio  # type: ignore
diff --git a/google/cloud/asset_v1p2beta1/types/asset_service.py b/google/cloud/asset_v1p2beta1/types/asset_service.py
index e02b95f9..e153d6e1 100644
--- a/google/cloud/asset_v1p2beta1/types/asset_service.py
+++ b/google/cloud/asset_v1p2beta1/types/asset_service.py
@@ -154,9 +154,12 @@ class DeleteFeedRequest(proto.Message):
 class OutputConfig(proto.Message):
     r"""Output configuration for export assets destination.
 
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         gcs_destination (google.cloud.asset_v1p2beta1.types.GcsDestination):
             Destination on Cloud Storage.
+            This field is a member of `oneof`_ ``destination``.
     """
 
     gcs_destination = proto.Field(
@@ -167,6 +170,8 @@ class OutputConfig(proto.Message):
 class GcsDestination(proto.Message):
     r"""A Cloud Storage location.
 
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         uri (str):
             The uri of the Cloud Storage object. It's the same uri that
@@ -175,6 +180,7 @@ class GcsDestination(proto.Message):
             Object
             Metadata <https://cloud.google.com/storage/docs/viewing-editing-metadata>`__
             for more information.
+            This field is a member of `oneof`_ ``object_uri``.
     """
 
     uri = proto.Field(proto.STRING, number=1, oneof="object_uri",)
@@ -195,9 +201,12 @@ class PubsubDestination(proto.Message):
 class FeedOutputConfig(proto.Message):
     r"""Output configuration for asset feed destination.
 
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         pubsub_destination (google.cloud.asset_v1p2beta1.types.PubsubDestination):
             Destination on Cloud Pubsub.
+            This field is a member of `oneof`_ ``destination``.
     """
 
     pubsub_destination = proto.Field(
diff --git a/google/cloud/asset_v1p4beta1/services/asset_service/async_client.py b/google/cloud/asset_v1p4beta1/services/asset_service/async_client.py
index 709172f6..9c2b1a20 100644
--- a/google/cloud/asset_v1p4beta1/services/asset_service/async_client.py
+++ b/google/cloud/asset_v1p4beta1/services/asset_service/async_client.py
@@ -19,13 +19,15 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-import google.api_core.client_options as ClientOptions  # type: ignore
+from google.api_core.client_options import ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.api_core import operation  # type: ignore
 from google.api_core import operation_async  # type: ignore
 from google.cloud.asset_v1p4beta1.types import asset_service
@@ -159,9 +161,9 @@ def __init__(
 
     async def analyze_iam_policy(
         self,
-        request: asset_service.AnalyzeIamPolicyRequest = None,
+        request: Union[asset_service.AnalyzeIamPolicyRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.AnalyzeIamPolicyResponse:
@@ -171,7 +173,7 @@ async def analyze_iam_policy(
         matching the request.
 
         Args:
-            request (:class:`google.cloud.asset_v1p4beta1.types.AnalyzeIamPolicyRequest`):
+            request (Union[google.cloud.asset_v1p4beta1.types.AnalyzeIamPolicyRequest, dict]):
                 The request object. A request message for
                 [AssetService.AnalyzeIamPolicy][google.cloud.asset.v1p4beta1.AssetService.AnalyzeIamPolicy].
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
@@ -222,9 +224,9 @@ async def analyze_iam_policy(
 
     async def export_iam_policy_analysis(
         self,
-        request: asset_service.ExportIamPolicyAnalysisRequest = None,
+        request: Union[asset_service.ExportIamPolicyAnalysisRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation_async.AsyncOperation:
@@ -235,7 +237,7 @@ async def export_iam_policy_analysis(
         the request to help callers to map responses to requests.
 
         Args:
-            request (:class:`google.cloud.asset_v1p4beta1.types.ExportIamPolicyAnalysisRequest`):
+            request (Union[google.cloud.asset_v1p4beta1.types.ExportIamPolicyAnalysisRequest, dict]):
                 The request object. A request message for
                 [AssetService.ExportIamPolicyAnalysis][google.cloud.asset.v1p4beta1.AssetService.ExportIamPolicyAnalysis].
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
diff --git a/google/cloud/asset_v1p4beta1/services/asset_service/client.py b/google/cloud/asset_v1p4beta1/services/asset_service/client.py
index 11a73dd2..f0952ed3 100644
--- a/google/cloud/asset_v1p4beta1/services/asset_service/client.py
+++ b/google/cloud/asset_v1p4beta1/services/asset_service/client.py
@@ -30,6 +30,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.api_core import operation  # type: ignore
 from google.api_core import operation_async  # type: ignore
 from google.cloud.asset_v1p4beta1.types import asset_service
@@ -335,7 +337,7 @@ def analyze_iam_policy(
         self,
         request: Union[asset_service.AnalyzeIamPolicyRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> asset_service.AnalyzeIamPolicyResponse:
@@ -390,7 +392,7 @@ def export_iam_policy_analysis(
         self,
         request: Union[asset_service.ExportIamPolicyAnalysisRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> operation.Operation:
diff --git a/google/cloud/asset_v1p4beta1/services/asset_service/transports/base.py b/google/cloud/asset_v1p4beta1/services/asset_service/transports/base.py
index a2dc71f9..54e6267e 100644
--- a/google/cloud/asset_v1p4beta1/services/asset_service/transports/base.py
+++ b/google/cloud/asset_v1p4beta1/services/asset_service/transports/base.py
@@ -15,7 +15,6 @@
 #
 import abc
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Union
-import packaging.version
 import pkg_resources
 
 import google.auth  # type: ignore
@@ -37,15 +36,6 @@
 except pkg_resources.DistributionNotFound:
     DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo()
 
-try:
-    # google.auth.__version__ was added in 1.26.0
-    _GOOGLE_AUTH_VERSION = google.auth.__version__
-except AttributeError:
-    try:  # try pkg_resources if it is available
-        _GOOGLE_AUTH_VERSION = pkg_resources.get_distribution("google-auth").version
-    except pkg_resources.DistributionNotFound:  # pragma: NO COVER
-        _GOOGLE_AUTH_VERSION = None
-
 
 class AssetServiceTransport(abc.ABC):
     """Abstract transport class for AssetService."""
@@ -95,7 +85,7 @@ def __init__(
             host += ":443"
         self._host = host
 
-        scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
+        scopes_kwargs = {"scopes": scopes, "default_scopes": self.AUTH_SCOPES}
 
         # Save the scopes.
         self._scopes = scopes
@@ -128,29 +118,6 @@ def __init__(
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): This method is in the base transport
-    # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-auth is increased.
-
-    # TODO: Remove this function once google-auth >= 1.25.0 is required
-    @classmethod
-    def _get_scopes_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Optional[Sequence[str]]]:
-        """Returns scopes kwargs to pass to google-auth methods depending on the google-auth version"""
-
-        scopes_kwargs = {}
-
-        if _GOOGLE_AUTH_VERSION and (
-            packaging.version.parse(_GOOGLE_AUTH_VERSION)
-            >= packaging.version.parse("1.25.0")
-        ):
-            scopes_kwargs = {"scopes": scopes, "default_scopes": cls.AUTH_SCOPES}
-        else:
-            scopes_kwargs = {"scopes": scopes or cls.AUTH_SCOPES}
-
-        return scopes_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
@@ -185,7 +152,7 @@ def close(self):
         raise NotImplementedError()
 
     @property
-    def operations_client(self) -> operations_v1.OperationsClient:
+    def operations_client(self):
         """Return the client designed to process long-running operations."""
         raise NotImplementedError()
 
diff --git a/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc.py b/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc.py
index ebfb7155..9a6bb977 100644
--- a/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc.py
+++ b/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc.py
@@ -112,7 +112,7 @@ def __init__(
         self._grpc_channel = None
         self._ssl_channel_credentials = ssl_channel_credentials
         self._stubs: Dict[str, Callable] = {}
-        self._operations_client = None
+        self._operations_client: Optional[operations_v1.OperationsClient] = None
 
         if api_mtls_endpoint:
             warnings.warn("api_mtls_endpoint is deprecated", DeprecationWarning)
diff --git a/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc_asyncio.py b/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc_asyncio.py
index a39ed4f9..eedf154c 100644
--- a/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc_asyncio.py
+++ b/google/cloud/asset_v1p4beta1/services/asset_service/transports/grpc_asyncio.py
@@ -21,7 +21,6 @@
 from google.api_core import operations_v1  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
-import packaging.version
 
 import grpc  # type: ignore
 from grpc.experimental import aio  # type: ignore
@@ -159,7 +158,7 @@ def __init__(
         self._grpc_channel = None
         self._ssl_channel_credentials = ssl_channel_credentials
         self._stubs: Dict[str, Callable] = {}
-        self._operations_client = None
+        self._operations_client: Optional[operations_v1.OperationsAsyncClient] = None
 
         if api_mtls_endpoint:
             warnings.warn("api_mtls_endpoint is deprecated", DeprecationWarning)
diff --git a/google/cloud/asset_v1p4beta1/types/asset_service.py b/google/cloud/asset_v1p4beta1/types/asset_service.py
index d54f88b7..f29125fd 100644
--- a/google/cloud/asset_v1p4beta1/types/asset_service.py
+++ b/google/cloud/asset_v1p4beta1/types/asset_service.py
@@ -287,9 +287,13 @@ class IamPolicyAnalysisOutputConfig(proto.Message):
     r"""Output configuration for export IAM policy analysis
     destination.
 
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         gcs_destination (google.cloud.asset_v1p4beta1.types.IamPolicyAnalysisOutputConfig.GcsDestination):
             Destination on Cloud Storage.
+            This field is a member of `oneof`_ ``destination``.
     """
 
     class GcsDestination(proto.Message):
diff --git a/google/cloud/asset_v1p4beta1/types/assets.py b/google/cloud/asset_v1p4beta1/types/assets.py
index b3730ac7..9fcb1961 100644
--- a/google/cloud/asset_v1p4beta1/types/assets.py
+++ b/google/cloud/asset_v1p4beta1/types/assets.py
@@ -93,11 +93,20 @@ class Resource(proto.Message):
     class Access(proto.Message):
         r"""A role or permission that appears in an access control list.
 
+        This message has `oneof`_ fields (mutually exclusive fields).
+        For each oneof, at most one member field can be set at the same time.
+        Setting any member of the oneof automatically clears all other
+        members.
+
+        .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
         Attributes:
             role (str):
                 The role.
+                This field is a member of `oneof`_ ``oneof_access``.
             permission (str):
                 The permission.
+                This field is a member of `oneof`_ ``oneof_access``.
             analysis_state (google.cloud.asset_v1p4beta1.types.IamPolicyAnalysisResult.AnalysisState):
                 The analysis state of this access node.
         """
diff --git a/google/cloud/asset_v1p5beta1/services/asset_service/async_client.py b/google/cloud/asset_v1p5beta1/services/asset_service/async_client.py
index 26f0eb77..100870d1 100644
--- a/google/cloud/asset_v1p5beta1/services/asset_service/async_client.py
+++ b/google/cloud/asset_v1p5beta1/services/asset_service/async_client.py
@@ -19,13 +19,15 @@
 from typing import Dict, Sequence, Tuple, Type, Union
 import pkg_resources
 
-import google.api_core.client_options as ClientOptions  # type: ignore
+from google.api_core.client_options import ClientOptions  # type: ignore
 from google.api_core import exceptions as core_exceptions  # type: ignore
 from google.api_core import gapic_v1  # type: ignore
 from google.api_core import retry as retries  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.asset_v1p5beta1.services.asset_service import pagers
 from google.cloud.asset_v1p5beta1.types import asset_service
 from google.cloud.asset_v1p5beta1.types import assets
@@ -168,9 +170,9 @@ def __init__(
 
     async def list_assets(
         self,
-        request: asset_service.ListAssetsRequest = None,
+        request: Union[asset_service.ListAssetsRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListAssetsAsyncPager:
@@ -178,7 +180,7 @@ async def list_assets(
         paged results in response.
 
         Args:
-            request (:class:`google.cloud.asset_v1p5beta1.types.ListAssetsRequest`):
+            request (Union[google.cloud.asset_v1p5beta1.types.ListAssetsRequest, dict]):
                 The request object. ListAssets request.
             retry (google.api_core.retry.Retry): Designation of what errors, if any,
                 should be retried.
diff --git a/google/cloud/asset_v1p5beta1/services/asset_service/client.py b/google/cloud/asset_v1p5beta1/services/asset_service/client.py
index 3fa2f980..7e551fb0 100644
--- a/google/cloud/asset_v1p5beta1/services/asset_service/client.py
+++ b/google/cloud/asset_v1p5beta1/services/asset_service/client.py
@@ -30,6 +30,8 @@
 from google.auth.exceptions import MutualTLSChannelError  # type: ignore
 from google.oauth2 import service_account  # type: ignore
 
+OptionalRetry = Union[retries.Retry, object]
+
 from google.cloud.asset_v1p5beta1.services.asset_service import pagers
 from google.cloud.asset_v1p5beta1.types import asset_service
 from google.cloud.asset_v1p5beta1.types import assets
@@ -382,7 +384,7 @@ def list_assets(
         self,
         request: Union[asset_service.ListAssetsRequest, dict] = None,
         *,
-        retry: retries.Retry = gapic_v1.method.DEFAULT,
+        retry: OptionalRetry = gapic_v1.method.DEFAULT,
         timeout: float = None,
         metadata: Sequence[Tuple[str, str]] = (),
     ) -> pagers.ListAssetsPager:
diff --git a/google/cloud/asset_v1p5beta1/services/asset_service/transports/base.py b/google/cloud/asset_v1p5beta1/services/asset_service/transports/base.py
index 4a6c651a..7ac6d3b2 100644
--- a/google/cloud/asset_v1p5beta1/services/asset_service/transports/base.py
+++ b/google/cloud/asset_v1p5beta1/services/asset_service/transports/base.py
@@ -15,7 +15,6 @@
 #
 import abc
 from typing import Awaitable, Callable, Dict, Optional, Sequence, Union
-import packaging.version
 import pkg_resources
 
 import google.auth  # type: ignore
@@ -35,15 +34,6 @@
 except pkg_resources.DistributionNotFound:
     DEFAULT_CLIENT_INFO = gapic_v1.client_info.ClientInfo()
 
-try:
-    # google.auth.__version__ was added in 1.26.0
-    _GOOGLE_AUTH_VERSION = google.auth.__version__
-except AttributeError:
-    try:  # try pkg_resources if it is available
-        _GOOGLE_AUTH_VERSION = pkg_resources.get_distribution("google-auth").version
-    except pkg_resources.DistributionNotFound:  # pragma: NO COVER
-        _GOOGLE_AUTH_VERSION = None
-
 
 class AssetServiceTransport(abc.ABC):
     """Abstract transport class for AssetService."""
@@ -93,7 +83,7 @@ def __init__(
             host += ":443"
         self._host = host
 
-        scopes_kwargs = self._get_scopes_kwargs(self._host, scopes)
+        scopes_kwargs = {"scopes": scopes, "default_scopes": self.AUTH_SCOPES}
 
         # Save the scopes.
         self._scopes = scopes
@@ -126,29 +116,6 @@ def __init__(
         # Save the credentials.
         self._credentials = credentials
 
-    # TODO(busunkim): This method is in the base transport
-    # to avoid duplicating code across the transport classes. These functions
-    # should be deleted once the minimum required versions of google-auth is increased.
-
-    # TODO: Remove this function once google-auth >= 1.25.0 is required
-    @classmethod
-    def _get_scopes_kwargs(
-        cls, host: str, scopes: Optional[Sequence[str]]
-    ) -> Dict[str, Optional[Sequence[str]]]:
-        """Returns scopes kwargs to pass to google-auth methods depending on the google-auth version"""
-
-        scopes_kwargs = {}
-
-        if _GOOGLE_AUTH_VERSION and (
-            packaging.version.parse(_GOOGLE_AUTH_VERSION)
-            >= packaging.version.parse("1.25.0")
-        ):
-            scopes_kwargs = {"scopes": scopes, "default_scopes": cls.AUTH_SCOPES}
-        else:
-            scopes_kwargs = {"scopes": scopes or cls.AUTH_SCOPES}
-
-        return scopes_kwargs
-
     def _prep_wrapped_messages(self, client_info):
         # Precompute the wrapped methods.
         self._wrapped_methods = {
diff --git a/google/cloud/asset_v1p5beta1/services/asset_service/transports/grpc_asyncio.py b/google/cloud/asset_v1p5beta1/services/asset_service/transports/grpc_asyncio.py
index 5fd7fa7e..fa53920d 100644
--- a/google/cloud/asset_v1p5beta1/services/asset_service/transports/grpc_asyncio.py
+++ b/google/cloud/asset_v1p5beta1/services/asset_service/transports/grpc_asyncio.py
@@ -20,7 +20,6 @@
 from google.api_core import grpc_helpers_async  # type: ignore
 from google.auth import credentials as ga_credentials  # type: ignore
 from google.auth.transport.grpc import SslCredentials  # type: ignore
-import packaging.version
 
 import grpc  # type: ignore
 from grpc.experimental import aio  # type: ignore
diff --git a/google/cloud/asset_v1p5beta1/types/assets.py b/google/cloud/asset_v1p5beta1/types/assets.py
index 759713cb..988c127a 100644
--- a/google/cloud/asset_v1p5beta1/types/assets.py
+++ b/google/cloud/asset_v1p5beta1/types/assets.py
@@ -32,6 +32,13 @@ class Asset(proto.Message):
     r"""Cloud asset. This includes all Google Cloud Platform
     resources, Cloud IAM policies, and other non-GCP assets.
 
+    This message has `oneof`_ fields (mutually exclusive fields).
+    For each oneof, at most one member field can be set at the same time.
+    Setting any member of the oneof automatically clears all other
+    members.
+
+    .. _oneof: https://proto-plus-python.readthedocs.io/en/stable/fields.html#oneofs-mutually-exclusive-fields
+
     Attributes:
         name (str):
             The full name of the asset. For example:
@@ -56,10 +63,13 @@ class Asset(proto.Message):
             different constraints.
         access_policy (google.identity.accesscontextmanager.v1.access_policy_pb2.AccessPolicy):
 
+            This field is a member of `oneof`_ ``access_context_policy``.
         access_level (google.identity.accesscontextmanager.v1.access_level_pb2.AccessLevel):
 
+            This field is a member of `oneof`_ ``access_context_policy``.
         service_perimeter (google.identity.accesscontextmanager.v1.service_perimeter_pb2.ServicePerimeter):
 
+            This field is a member of `oneof`_ ``access_context_policy``.
         ancestors (Sequence[str]):
             Asset's ancestry path in Cloud Resource Manager (CRM)
             hierarchy, represented as a list of relative resource names.
diff --git a/setup.py b/setup.py
index f44f6eb0..d30ba321 100644
--- a/setup.py
+++ b/setup.py
@@ -31,13 +31,12 @@
     # NOTE: Maintainers, please do not require google-api-core>=2.x.x
     # Until this issue is closed
     # https://github.com/googleapis/google-cloud-python/issues/10566
-    "google-api-core[grpc] >= 1.26.0, <3.0.0dev",
+    "google-api-core[grpc] >= 1.28.0, <3.0.0dev",
     "grpc-google-iam-v1 >= 0.12.3, < 0.13dev",
     "google-cloud-access-context-manager >= 0.1.2, < 0.2.0dev",
     "google-cloud-org-policy>=0.1.2, <2.0.0",
     "google-cloud-os-config >= 1.0.0, <2.0.0dev",
     "proto-plus >= 1.10.0",
-    "packaging >= 14.3",
 ]
 
 extras = {"libcst": "libcst >= 0.2.5"}
@@ -88,7 +87,7 @@
     packages=packages,
     namespace_packages=namespaces,
     install_requires=dependencies,
-    extras_requires=extras,
+    extras_require=extras,
     python_requires=">=3.6",
     scripts=[
         "scripts/fixup_asset_v1_keywords.py",
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index d2b9a053..406bdb7e 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -5,12 +5,10 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-google-api-core==1.26.0
+google-api-core==1.28.0
 grpc-google-iam-v1==0.12.3
 google-cloud-access-context-manager==0.1.2
 google-cloud-org-policy==0.1.2
 google-cloud-os-config==1.0.0
 proto-plus==1.10.0
 libcst==0.2.5
-packaging==14.3
-google-auth==1.24.0  # TODO: remove when google-auth>=1.25.0 is required transitively through google-api-core
diff --git a/tests/unit/gapic/asset_v1/test_asset_service.py b/tests/unit/gapic/asset_v1/test_asset_service.py
index 01e68d22..4ad014a4 100644
--- a/tests/unit/gapic/asset_v1/test_asset_service.py
+++ b/tests/unit/gapic/asset_v1/test_asset_service.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -39,9 +38,6 @@
 from google.cloud.asset_v1.services.asset_service import AssetServiceClient
 from google.cloud.asset_v1.services.asset_service import pagers
 from google.cloud.asset_v1.services.asset_service import transports
-from google.cloud.asset_v1.services.asset_service.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.asset_v1.types import asset_service
 from google.cloud.asset_v1.types import assets
 from google.longrunning import operations_pb2
@@ -53,20 +49,6 @@
 import google.auth
 
 
-# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
-# through google-api-core:
-# - Delete the auth "less than" test cases
-# - Delete these pytest markers (Make the "greater than or equal to" tests the default).
-requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth < 1.25.0",
-)
-requires_google_auth_gte_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) < packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth >= 1.25.0",
-)
-
-
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
 
@@ -214,7 +196,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(api_endpoint="squid.clam.whelk")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -231,7 +213,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "never"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -248,7 +230,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "always"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -277,7 +259,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(quota_project_id="octopus")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -334,7 +316,7 @@ def test_asset_service_client_mtls_env_auto(
         )
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class(client_options=options)
+            client = client_class(transport=transport_name, client_options=options)
 
             if use_client_cert_env == "false":
                 expected_client_cert_source = None
@@ -376,7 +358,7 @@ def test_asset_service_client_mtls_env_auto(
                         expected_client_cert_source = client_cert_source_callback
 
                     patched.return_value = None
-                    client = client_class()
+                    client = client_class(transport=transport_name)
                     patched.assert_called_once_with(
                         credentials=None,
                         credentials_file=None,
@@ -398,7 +380,7 @@ def test_asset_service_client_mtls_env_auto(
                 return_value=False,
             ):
                 patched.return_value = None
-                client = client_class()
+                client = client_class(transport=transport_name)
                 patched.assert_called_once_with(
                     credentials=None,
                     credentials_file=None,
@@ -429,7 +411,7 @@ def test_asset_service_client_client_options_scopes(
     options = client_options.ClientOptions(scopes=["1", "2"],)
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -460,7 +442,7 @@ def test_asset_service_client_client_options_credentials_file(
     options = client_options.ClientOptions(credentials_file="credentials.json")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file="credentials.json",
@@ -3416,7 +3398,6 @@ def test_asset_service_base_transport():
         transport.operations_client
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -3437,26 +3418,6 @@ def test_asset_service_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_base_transport_with_credentials_file_old_google_auth():
-    # Instantiate the base transport with a credentials file
-    with mock.patch.object(
-        google.auth, "load_credentials_from_file", autospec=True
-    ) as load_creds, mock.patch(
-        "google.cloud.asset_v1.services.asset_service.transports.AssetServiceTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.AssetServiceTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 def test_asset_service_base_transport_with_adc():
     # Test the default credentials are used if credentials and credentials_file are None.
     with mock.patch.object(google.auth, "default", autospec=True) as adc, mock.patch(
@@ -3468,7 +3429,6 @@ def test_asset_service_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -3481,18 +3441,6 @@ def test_asset_service_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_auth_adc_old_google_auth():
-    # If no credentials are provided, we should use ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        AssetServiceClient()
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -3500,7 +3448,6 @@ def test_asset_service_auth_adc_old_google_auth():
         transports.AssetServiceGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_asset_service_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -3514,26 +3461,6 @@ def test_asset_service_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.AssetServiceGrpcTransport,
-        transports.AssetServiceGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_asset_service_transport_auth_adc_old_google_auth(transport_class):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport_class(quota_project_id="octopus")
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [
diff --git a/tests/unit/gapic/asset_v1p1beta1/test_asset_service.py b/tests/unit/gapic/asset_v1p1beta1/test_asset_service.py
index c25e6960..abe7fa94 100644
--- a/tests/unit/gapic/asset_v1p1beta1/test_asset_service.py
+++ b/tests/unit/gapic/asset_v1p1beta1/test_asset_service.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -36,29 +35,12 @@
 from google.cloud.asset_v1p1beta1.services.asset_service import AssetServiceClient
 from google.cloud.asset_v1p1beta1.services.asset_service import pagers
 from google.cloud.asset_v1p1beta1.services.asset_service import transports
-from google.cloud.asset_v1p1beta1.services.asset_service.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.asset_v1p1beta1.types import asset_service
 from google.cloud.asset_v1p1beta1.types import assets
 from google.oauth2 import service_account
 import google.auth
 
 
-# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
-# through google-api-core:
-# - Delete the auth "less than" test cases
-# - Delete these pytest markers (Make the "greater than or equal to" tests the default).
-requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth < 1.25.0",
-)
-requires_google_auth_gte_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) < packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth >= 1.25.0",
-)
-
-
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
 
@@ -206,7 +188,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(api_endpoint="squid.clam.whelk")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -223,7 +205,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "never"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -240,7 +222,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "always"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -269,7 +251,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(quota_project_id="octopus")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -326,7 +308,7 @@ def test_asset_service_client_mtls_env_auto(
         )
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class(client_options=options)
+            client = client_class(transport=transport_name, client_options=options)
 
             if use_client_cert_env == "false":
                 expected_client_cert_source = None
@@ -368,7 +350,7 @@ def test_asset_service_client_mtls_env_auto(
                         expected_client_cert_source = client_cert_source_callback
 
                     patched.return_value = None
-                    client = client_class()
+                    client = client_class(transport=transport_name)
                     patched.assert_called_once_with(
                         credentials=None,
                         credentials_file=None,
@@ -390,7 +372,7 @@ def test_asset_service_client_mtls_env_auto(
                 return_value=False,
             ):
                 patched.return_value = None
-                client = client_class()
+                client = client_class(transport=transport_name)
                 patched.assert_called_once_with(
                     credentials=None,
                     credentials_file=None,
@@ -421,7 +403,7 @@ def test_asset_service_client_client_options_scopes(
     options = client_options.ClientOptions(scopes=["1", "2"],)
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -452,7 +434,7 @@ def test_asset_service_client_client_options_credentials_file(
     options = client_options.ClientOptions(credentials_file="credentials.json")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file="credentials.json",
@@ -1377,7 +1359,6 @@ def test_asset_service_base_transport():
         transport.close()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -1398,26 +1379,6 @@ def test_asset_service_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_base_transport_with_credentials_file_old_google_auth():
-    # Instantiate the base transport with a credentials file
-    with mock.patch.object(
-        google.auth, "load_credentials_from_file", autospec=True
-    ) as load_creds, mock.patch(
-        "google.cloud.asset_v1p1beta1.services.asset_service.transports.AssetServiceTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.AssetServiceTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 def test_asset_service_base_transport_with_adc():
     # Test the default credentials are used if credentials and credentials_file are None.
     with mock.patch.object(google.auth, "default", autospec=True) as adc, mock.patch(
@@ -1429,7 +1390,6 @@ def test_asset_service_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -1442,18 +1402,6 @@ def test_asset_service_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_auth_adc_old_google_auth():
-    # If no credentials are provided, we should use ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        AssetServiceClient()
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -1461,7 +1409,6 @@ def test_asset_service_auth_adc_old_google_auth():
         transports.AssetServiceGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_asset_service_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -1475,26 +1422,6 @@ def test_asset_service_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.AssetServiceGrpcTransport,
-        transports.AssetServiceGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_asset_service_transport_auth_adc_old_google_auth(transport_class):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport_class(quota_project_id="octopus")
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [
diff --git a/tests/unit/gapic/asset_v1p2beta1/test_asset_service.py b/tests/unit/gapic/asset_v1p2beta1/test_asset_service.py
index 7a60b166..6997e64b 100644
--- a/tests/unit/gapic/asset_v1p2beta1/test_asset_service.py
+++ b/tests/unit/gapic/asset_v1p2beta1/test_asset_service.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -35,29 +34,12 @@
 from google.cloud.asset_v1p2beta1.services.asset_service import AssetServiceAsyncClient
 from google.cloud.asset_v1p2beta1.services.asset_service import AssetServiceClient
 from google.cloud.asset_v1p2beta1.services.asset_service import transports
-from google.cloud.asset_v1p2beta1.services.asset_service.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.asset_v1p2beta1.types import asset_service
 from google.oauth2 import service_account
 from google.protobuf import field_mask_pb2  # type: ignore
 import google.auth
 
 
-# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
-# through google-api-core:
-# - Delete the auth "less than" test cases
-# - Delete these pytest markers (Make the "greater than or equal to" tests the default).
-requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth < 1.25.0",
-)
-requires_google_auth_gte_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) < packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth >= 1.25.0",
-)
-
-
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
 
@@ -205,7 +187,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(api_endpoint="squid.clam.whelk")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -222,7 +204,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "never"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -239,7 +221,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "always"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -268,7 +250,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(quota_project_id="octopus")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -325,7 +307,7 @@ def test_asset_service_client_mtls_env_auto(
         )
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class(client_options=options)
+            client = client_class(transport=transport_name, client_options=options)
 
             if use_client_cert_env == "false":
                 expected_client_cert_source = None
@@ -367,7 +349,7 @@ def test_asset_service_client_mtls_env_auto(
                         expected_client_cert_source = client_cert_source_callback
 
                     patched.return_value = None
-                    client = client_class()
+                    client = client_class(transport=transport_name)
                     patched.assert_called_once_with(
                         credentials=None,
                         credentials_file=None,
@@ -389,7 +371,7 @@ def test_asset_service_client_mtls_env_auto(
                 return_value=False,
             ):
                 patched.return_value = None
-                client = client_class()
+                client = client_class(transport=transport_name)
                 patched.assert_called_once_with(
                     credentials=None,
                     credentials_file=None,
@@ -420,7 +402,7 @@ def test_asset_service_client_client_options_scopes(
     options = client_options.ClientOptions(scopes=["1", "2"],)
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -451,7 +433,7 @@ def test_asset_service_client_client_options_credentials_file(
     options = client_options.ClientOptions(credentials_file="credentials.json")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file="credentials.json",
@@ -1599,7 +1581,6 @@ def test_asset_service_base_transport():
         transport.close()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -1620,26 +1601,6 @@ def test_asset_service_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_base_transport_with_credentials_file_old_google_auth():
-    # Instantiate the base transport with a credentials file
-    with mock.patch.object(
-        google.auth, "load_credentials_from_file", autospec=True
-    ) as load_creds, mock.patch(
-        "google.cloud.asset_v1p2beta1.services.asset_service.transports.AssetServiceTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.AssetServiceTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 def test_asset_service_base_transport_with_adc():
     # Test the default credentials are used if credentials and credentials_file are None.
     with mock.patch.object(google.auth, "default", autospec=True) as adc, mock.patch(
@@ -1651,7 +1612,6 @@ def test_asset_service_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -1664,18 +1624,6 @@ def test_asset_service_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_auth_adc_old_google_auth():
-    # If no credentials are provided, we should use ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        AssetServiceClient()
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -1683,7 +1631,6 @@ def test_asset_service_auth_adc_old_google_auth():
         transports.AssetServiceGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_asset_service_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -1697,26 +1644,6 @@ def test_asset_service_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.AssetServiceGrpcTransport,
-        transports.AssetServiceGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_asset_service_transport_auth_adc_old_google_auth(transport_class):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport_class(quota_project_id="octopus")
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [
diff --git a/tests/unit/gapic/asset_v1p4beta1/test_asset_service.py b/tests/unit/gapic/asset_v1p4beta1/test_asset_service.py
index f8ab8132..4a7de233 100644
--- a/tests/unit/gapic/asset_v1p4beta1/test_asset_service.py
+++ b/tests/unit/gapic/asset_v1p4beta1/test_asset_service.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -38,9 +37,6 @@
 from google.cloud.asset_v1p4beta1.services.asset_service import AssetServiceAsyncClient
 from google.cloud.asset_v1p4beta1.services.asset_service import AssetServiceClient
 from google.cloud.asset_v1p4beta1.services.asset_service import transports
-from google.cloud.asset_v1p4beta1.services.asset_service.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.asset_v1p4beta1.types import asset_service
 from google.cloud.asset_v1p4beta1.types import assets
 from google.longrunning import operations_pb2
@@ -49,20 +45,6 @@
 import google.auth
 
 
-# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
-# through google-api-core:
-# - Delete the auth "less than" test cases
-# - Delete these pytest markers (Make the "greater than or equal to" tests the default).
-requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth < 1.25.0",
-)
-requires_google_auth_gte_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) < packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth >= 1.25.0",
-)
-
-
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
 
@@ -210,7 +192,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(api_endpoint="squid.clam.whelk")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -227,7 +209,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "never"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -244,7 +226,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "always"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -273,7 +255,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(quota_project_id="octopus")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -330,7 +312,7 @@ def test_asset_service_client_mtls_env_auto(
         )
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class(client_options=options)
+            client = client_class(transport=transport_name, client_options=options)
 
             if use_client_cert_env == "false":
                 expected_client_cert_source = None
@@ -372,7 +354,7 @@ def test_asset_service_client_mtls_env_auto(
                         expected_client_cert_source = client_cert_source_callback
 
                     patched.return_value = None
-                    client = client_class()
+                    client = client_class(transport=transport_name)
                     patched.assert_called_once_with(
                         credentials=None,
                         credentials_file=None,
@@ -394,7 +376,7 @@ def test_asset_service_client_mtls_env_auto(
                 return_value=False,
             ):
                 patched.return_value = None
-                client = client_class()
+                client = client_class(transport=transport_name)
                 patched.assert_called_once_with(
                     credentials=None,
                     credentials_file=None,
@@ -425,7 +407,7 @@ def test_asset_service_client_client_options_scopes(
     options = client_options.ClientOptions(scopes=["1", "2"],)
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -456,7 +438,7 @@ def test_asset_service_client_client_options_credentials_file(
     options = client_options.ClientOptions(credentials_file="credentials.json")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file="credentials.json",
@@ -895,7 +877,6 @@ def test_asset_service_base_transport():
         transport.operations_client
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -916,26 +897,6 @@ def test_asset_service_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_base_transport_with_credentials_file_old_google_auth():
-    # Instantiate the base transport with a credentials file
-    with mock.patch.object(
-        google.auth, "load_credentials_from_file", autospec=True
-    ) as load_creds, mock.patch(
-        "google.cloud.asset_v1p4beta1.services.asset_service.transports.AssetServiceTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.AssetServiceTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 def test_asset_service_base_transport_with_adc():
     # Test the default credentials are used if credentials and credentials_file are None.
     with mock.patch.object(google.auth, "default", autospec=True) as adc, mock.patch(
@@ -947,7 +908,6 @@ def test_asset_service_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -960,18 +920,6 @@ def test_asset_service_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_auth_adc_old_google_auth():
-    # If no credentials are provided, we should use ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        AssetServiceClient()
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -979,7 +927,6 @@ def test_asset_service_auth_adc_old_google_auth():
         transports.AssetServiceGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_asset_service_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -993,26 +940,6 @@ def test_asset_service_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.AssetServiceGrpcTransport,
-        transports.AssetServiceGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_asset_service_transport_auth_adc_old_google_auth(transport_class):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport_class(quota_project_id="octopus")
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [
diff --git a/tests/unit/gapic/asset_v1p5beta1/test_asset_service.py b/tests/unit/gapic/asset_v1p5beta1/test_asset_service.py
index b2c75ae9..ea6b47da 100644
--- a/tests/unit/gapic/asset_v1p5beta1/test_asset_service.py
+++ b/tests/unit/gapic/asset_v1p5beta1/test_asset_service.py
@@ -15,7 +15,6 @@
 #
 import os
 import mock
-import packaging.version
 
 import grpc
 from grpc.experimental import aio
@@ -36,9 +35,6 @@
 from google.cloud.asset_v1p5beta1.services.asset_service import AssetServiceClient
 from google.cloud.asset_v1p5beta1.services.asset_service import pagers
 from google.cloud.asset_v1p5beta1.services.asset_service import transports
-from google.cloud.asset_v1p5beta1.services.asset_service.transports.base import (
-    _GOOGLE_AUTH_VERSION,
-)
 from google.cloud.asset_v1p5beta1.types import asset_service
 from google.cloud.asset_v1p5beta1.types import assets
 from google.oauth2 import service_account
@@ -46,20 +42,6 @@
 import google.auth
 
 
-# TODO(busunkim): Once google-auth >= 1.25.0 is required transitively
-# through google-api-core:
-# - Delete the auth "less than" test cases
-# - Delete these pytest markers (Make the "greater than or equal to" tests the default).
-requires_google_auth_lt_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) >= packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth < 1.25.0",
-)
-requires_google_auth_gte_1_25_0 = pytest.mark.skipif(
-    packaging.version.parse(_GOOGLE_AUTH_VERSION) < packaging.version.parse("1.25.0"),
-    reason="This test requires google-auth >= 1.25.0",
-)
-
-
 def client_cert_source_callback():
     return b"cert bytes", b"key bytes"
 
@@ -207,7 +189,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(api_endpoint="squid.clam.whelk")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -224,7 +206,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "never"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -241,7 +223,7 @@ def test_asset_service_client_client_options(
     with mock.patch.dict(os.environ, {"GOOGLE_API_USE_MTLS_ENDPOINT": "always"}):
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class()
+            client = client_class(transport=transport_name)
             patched.assert_called_once_with(
                 credentials=None,
                 credentials_file=None,
@@ -270,7 +252,7 @@ def test_asset_service_client_client_options(
     options = client_options.ClientOptions(quota_project_id="octopus")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -327,7 +309,7 @@ def test_asset_service_client_mtls_env_auto(
         )
         with mock.patch.object(transport_class, "__init__") as patched:
             patched.return_value = None
-            client = client_class(client_options=options)
+            client = client_class(transport=transport_name, client_options=options)
 
             if use_client_cert_env == "false":
                 expected_client_cert_source = None
@@ -369,7 +351,7 @@ def test_asset_service_client_mtls_env_auto(
                         expected_client_cert_source = client_cert_source_callback
 
                     patched.return_value = None
-                    client = client_class()
+                    client = client_class(transport=transport_name)
                     patched.assert_called_once_with(
                         credentials=None,
                         credentials_file=None,
@@ -391,7 +373,7 @@ def test_asset_service_client_mtls_env_auto(
                 return_value=False,
             ):
                 patched.return_value = None
-                client = client_class()
+                client = client_class(transport=transport_name)
                 patched.assert_called_once_with(
                     credentials=None,
                     credentials_file=None,
@@ -422,7 +404,7 @@ def test_asset_service_client_client_options_scopes(
     options = client_options.ClientOptions(scopes=["1", "2"],)
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file=None,
@@ -453,7 +435,7 @@ def test_asset_service_client_client_options_credentials_file(
     options = client_options.ClientOptions(credentials_file="credentials.json")
     with mock.patch.object(transport_class, "__init__") as patched:
         patched.return_value = None
-        client = client_class(client_options=options)
+        client = client_class(transport=transport_name, client_options=options)
         patched.assert_called_once_with(
             credentials=None,
             credentials_file="credentials.json",
@@ -837,7 +819,6 @@ def test_asset_service_base_transport():
         transport.close()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_base_transport_with_credentials_file():
     # Instantiate the base transport with a credentials file
     with mock.patch.object(
@@ -858,26 +839,6 @@ def test_asset_service_base_transport_with_credentials_file():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_base_transport_with_credentials_file_old_google_auth():
-    # Instantiate the base transport with a credentials file
-    with mock.patch.object(
-        google.auth, "load_credentials_from_file", autospec=True
-    ) as load_creds, mock.patch(
-        "google.cloud.asset_v1p5beta1.services.asset_service.transports.AssetServiceTransport._prep_wrapped_messages"
-    ) as Transport:
-        Transport.return_value = None
-        load_creds.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport = transports.AssetServiceTransport(
-            credentials_file="credentials.json", quota_project_id="octopus",
-        )
-        load_creds.assert_called_once_with(
-            "credentials.json",
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 def test_asset_service_base_transport_with_adc():
     # Test the default credentials are used if credentials and credentials_file are None.
     with mock.patch.object(google.auth, "default", autospec=True) as adc, mock.patch(
@@ -889,7 +850,6 @@ def test_asset_service_base_transport_with_adc():
         adc.assert_called_once()
 
 
-@requires_google_auth_gte_1_25_0
 def test_asset_service_auth_adc():
     # If no credentials are provided, we should use ADC credentials.
     with mock.patch.object(google.auth, "default", autospec=True) as adc:
@@ -902,18 +862,6 @@ def test_asset_service_auth_adc():
         )
 
 
-@requires_google_auth_lt_1_25_0
-def test_asset_service_auth_adc_old_google_auth():
-    # If no credentials are provided, we should use ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        AssetServiceClient()
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id=None,
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class",
     [
@@ -921,7 +869,6 @@ def test_asset_service_auth_adc_old_google_auth():
         transports.AssetServiceGrpcAsyncIOTransport,
     ],
 )
-@requires_google_auth_gte_1_25_0
 def test_asset_service_transport_auth_adc(transport_class):
     # If credentials and host are not provided, the transport class should use
     # ADC credentials.
@@ -935,26 +882,6 @@ def test_asset_service_transport_auth_adc(transport_class):
         )
 
 
-@pytest.mark.parametrize(
-    "transport_class",
-    [
-        transports.AssetServiceGrpcTransport,
-        transports.AssetServiceGrpcAsyncIOTransport,
-    ],
-)
-@requires_google_auth_lt_1_25_0
-def test_asset_service_transport_auth_adc_old_google_auth(transport_class):
-    # If credentials and host are not provided, the transport class should use
-    # ADC credentials.
-    with mock.patch.object(google.auth, "default", autospec=True) as adc:
-        adc.return_value = (ga_credentials.AnonymousCredentials(), None)
-        transport_class(quota_project_id="octopus")
-        adc.assert_called_once_with(
-            scopes=("https://www.googleapis.com/auth/cloud-platform",),
-            quota_project_id="octopus",
-        )
-
-
 @pytest.mark.parametrize(
     "transport_class,grpc_helpers",
     [