function.

  Raises:
    FileExistsError: Iff `output_dir` is not empty and `overwrite` is false.
  """
  dir_not_empty = (
      output_dir is not None
      and file_io.file_exists_v2(output_dir)
      and file_io.list_directory_v2(output_dir)
  )

  if dir_not_empty and not overwrite:
    raise FileExistsError(
        f'Output directory already exists: {output_dir} . '

            preset_method=_PresetMethod.METHOD_DYNAMIC_RANGE_INT8
        ),
        tags=tags,
        signature_keys=['serving_default'],
    )

    with self.assertRaisesRegex(
        FileExistsError, 'Output directory already exists'
    ):
      quantize_model.quantize(
          self._input_saved_model_path,
          self._output_saved_model_path,
          quantization_options,
      )