docs: def extract_file_from_tar(bytes_io, expected_file):
      """extract a file from a bytes_io tar. Returns bytes"""
      with open('temp', 'wb+') as f:
          bytes_io.seek(0)
          shutil.copyfileobj(bytes_io, f, length=131072)
      tar = tarfile.open('temp', mode='r:gz')
      os.remove('temp')
      return tar.extractfile(expected_file).read()