code: def GetStructByteOrderString(self):
      
      if not self._data_type_definition:
        return None
  
      return self._BYTE_ORDER_STRINGS.get(
          self._data_type_definition.byte_order, None)
docs: Retrieves the Python struct format string.
  
      Returns:
        str: format string as used by Python struct or None if format string
            cannot be determined.