code: def format(self):
      if self._params["ext"] == "wav":
          return "WAV"
      if self._params["ext"] == "flac":
          return "FLAC"
      if self._params["ext"] == "ogg":
          return "OGG"
      if self._params["ext"] in ["sph", "nis", "nist"]:
          return "NIST"
  
imports: import os
  import tarfile
  from unittest.mock import patch
  import torch
  from parameterized import parameterized
  from torchaudio._internal import module_utils
  from torchaudio.backend import soundfile_backend
  from torchaudio_unittest.common_utils import get_wav_data, load_wav, normalize_wav, PytorchTestCase, save_wav, skipIfNoModule, TempDirMixin
  from .common import dtype2subtype, parameterize, skipIfFormatNotSupported
label_desc: Use image node_id 3 for calling the SoundFileMock obj's underlying member method code with example usage: obj.format() and returns: str, str, str, str