doc: torch.utils.data.Sampler: __len__ is optional

[kuraga]

Fixes #ISSUE_NUMBER

cc @andrewkho , @gokulavasan , @ejguan

[pytorch-bot]

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✅ You can merge normally! (3 Unrelated Failures)

As of commit da0b7a3 with merge base 53a64e4 ():

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

• pull / linux-focal-cuda12.1-py3.10-gcc9 / test (default, 2, 5, linux.4xlarge.nvidia.gpu) (gh) (similar failure)
  test_foreach.py::TestForeachCUDA::test_pointwise_op_with_tensor_of_scalarlist_overload__foreach_addcdiv_is_fastpath_False_cuda_bfloat16
• pull / linux-focal-py3.11-clang10 / test (dynamo, 2, 3, linux.2xlarge) (gh) (similar failure)
  functorch/test_aotdispatch.py::TestAOTAutograd::test_set__and_data_mutation_good
• pull / linux-focal-py3.12-clang10 / test (dynamo, 3, 3, linux.2xlarge) (gh) (similar failure)
  functorch/test_aotdispatch.py::TestAOTAutograd::test_set__and_data_mutation_good

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[kuraga]

Ping.

[andrewkho]

LGTM, we can land this once the CI is finished

[andrewkho]

@pytorchbot merge

[pytorchmergebot]

Merge failed

Reason: Approvers from one of the following sets are needed:

• superuser (pytorch/metamates)
• Core Reviewers (mruberry, lezcano, Skylion007, ngimel, peterbell10)
• Core Maintainers (soumith, gchanan, ezyang, dzhulgakov, malfet)

Details for Dev Infra team

Raised by workflow job

Failing merge rule: Core Maintainers

[andrewkho]

@pytorchbot merge

[pytorchmergebot]

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[kuraga]

Thanks!