docstr: self._info issues a warning when the subtype is unknown
  
  This will happen if a new subtype is supported in SoundFile: the _SUBTYPE_TO_BITS_PER_SAMPLE
  dict should be updated.
docstr_tok: ["self._info","issues","a","warning","when","the","subtype","is","unknown","This","will","happen","if","a","new","subtype","is","supported","in","SoundFile",":","the","_SUBTYPE_TO_BITS_PER_SAMPLE","dict","should","be","updated","."]
code: def test_unknown_subtype_warning(self):
      """self._info issues a warning when the subtype is unknown
  
      This will happen if a new subtype is supported in SoundFile: the _SUBTYPE_TO_BITS_PER_SAMPLE
      dict should be updated.
      """
  
      def _mock_info_func(_):
          class MockSoundFileInfo:
              samplerate = 8000
              frames = 356
              channels = 2
              subtype = "UNSEEN_SUBTYPE"
              format = "UNKNOWN"
  
          return MockSoundFileInfo()
  
      with patch("soundfile.info", _mock_info_func):
          with warnings.catch_warnings(record=True) as w:
              info = self._info("foo")
              assert len(w) == 1
              assert (
                  "UNSEEN_SUBTYPE subtype is unknown to TorchAudio"
                  in str(w[-1].message)
              )
              assert info.bits_per_sample == 0
  
imports: import tarfile
  import warnings
  from functools import partial
  from unittest.mock import patch
  import torch
  from torchaudio._backend.utils import get_info_func
  from torchaudio._internal import module_utils
  from torchaudio_unittest.backend.common import get_bits_per_sample, get_encoding
  from torchaudio_unittest.common_utils import get_wav_data, nested_params, PytorchTestCase, save_wav, skipIfNoModule, TempDirMixin
  from .common import parameterize, skipIfFormatNotSupported
label_desc: Use image node_id 5 for calling the TestInfo obj's underlying member method code with example usage: obj.test_unknown_subtype_warning() and returns: MockSoundFileInfo