code: def filename(self):
          
          client_id, __ = os.path.splitext(self.video.client_video_id)
          file_name = u'{name}-{language}.{format}'.format(
              name=client_id,
              language=self.language_code,
              format=self.file_format
          ).replace('\n', ' ')
          
          return file_name
docs: Returns readable filename for a transcript