def METHOD_NAME(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