Avoid crash when __doc__ is optimized away to None (-OO)

[FremyCompany]

When the python -OO flag is used, doc strings are no longer stored, and doc always returns None.

This makes the library fail at import time for a rather dubious reason.

It would be good to have this fixed.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/audio/3884

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[FremyCompany]

Also mentioned here:
https://discuss.pytorch.org/t/pr-torchaudio-incompatible-with-python-flag-oo-due-to-doc-being-none/216897/1

Note that the error message before the fix looks like this:

  File ".../.venv/lib/python3.12/site-packages/torio/io/_streaming_media_decoder.py", line 634, in StreamingMediaDecoder
    @_format_audio_args
     ^^^^^^^^^^^^^^^^^^
  File ".../.venv/lib/python3.12/site-packages/torio/io/_streaming_media_decoder.py", line 341, in decorator
    obj.__doc__ = obj.__doc__.format(**kwargs)
                  ^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'format'