docs(bigquery): consistent use of optional keyword

google/cloud/bigquery/_helpers.py

@@ -471,16 +471,16 @@ def _get_sub_prop(container, keys, default=None):
 
     This method works like ``dict.get(key)``, but for nested values.
 
-    Arguments:
+    Args:
         container (Dict):
             A dictionary which may contain other dictionaries as values.
         keys (Iterable):
             A sequence of keys to attempt to get the value for. Each item in
             the sequence represents a deeper nesting. The first key is for
             the top level. If there is a dictionary there, the second key
             attempts to get the value within that, and so on.
-        default (object):
-            (Optional) Value to returned if any of the keys are not found.
+        default (Optional[object]):
+            Value to returned if any of the keys are not found.
             Defaults to ``None``.
 
     Examples:
@@ -514,7 +514,7 @@ def _get_sub_prop(container, keys, default=None):
 def _set_sub_prop(container, keys, value):
     """Set a nested value in a dictionary.
 
-    Arguments:
+    Args:
         container (Dict):
             A dictionary which may contain other dictionaries as values.
         keys (Iterable):
@@ -557,7 +557,7 @@ def _set_sub_prop(container, keys, value):
 def _del_sub_prop(container, keys):
     """Remove a nested key fro a dictionary.
 
-    Arguments:
+    Args:
         container (Dict):
             A dictionary which may contain other dictionaries as values.
         keys (Iterable):

google/cloud/bigquery/_http.py

@@ -25,7 +25,7 @@ class Connection(_http.JSONConnection):
     Args:
         client (google.cloud.bigquery.client.Client): The client that owns the current connection.
 
-        client_info (google.api_core.client_info.ClientInfo): (Optional) instance used to generate user agent.
+        client_info (Optional[google.api_core.client_info.ClientInfo]): Instance used to generate user agent.
     """
 
     DEFAULT_API_ENDPOINT = "https://bigquery.googleapis.com"

google/cloud/bigquery/_pandas_helpers.py

@@ -472,10 +472,9 @@ def dataframe_to_parquet(dataframe, bq_schema, filepath, parquet_compression="SN
             columns in the DataFrame.
         filepath (str):
             Path to write Parquet file to.
-        parquet_compression (str):
-            (optional) The compression codec to use by the the
-            ``pyarrow.parquet.write_table`` serializing method. Defaults to
-            "SNAPPY".
+        parquet_compression (Optional[str]):
+            The compression codec to use by the the ``pyarrow.parquet.write_table``
+            serializing method. Defaults to "SNAPPY".
             https://arrow.apache.org/docs/python/generated/pyarrow.parquet.write_table.html#pyarrow-parquet-write-table
     """
     if pyarrow is None:

google/cloud/bigquery/dataset.py

@@ -295,9 +295,9 @@ def from_string(cls, dataset_id, default_project=None):
                 A dataset ID in standard SQL format. If ``default_project``
                 is not specified, this must include both the project ID and
                 the dataset ID, separated by ``.``.
-            default_project (str):
-                Optional. The project ID to use when ``dataset_id`` does not
-                include a project ID.
+            default_project (Optional[str]):
+                The project ID to use when ``dataset_id`` does not include a
+                project ID.
 
         Returns:
             DatasetReference: