code: def GetStructFormatString(self):
      
      if not self._element_data_type_map:
        return None
  
      number_of_elements = None
      if self._data_type_definition.elements_data_size:
        element_byte_size = self._element_data_type_definition.GetByteSize()
        if element_byte_size is None:
          return None
  
        number_of_elements, _ = divmod(
            self._data_type_definition.elements_data_size, element_byte_size)
  
      elif self._data_type_definition.number_of_elements:
        number_of_elements = self._data_type_definition.number_of_elements
  
      format_string = self._element_data_type_map.GetStructFormatString()
      if not number_of_elements or not format_string:
        return None
  
      return '{0:d}{1:s}'.format(number_of_elements, format_string)
docs: Retrieves the Python struct format string.
  
      Returns:
        str: format string as used by Python struct or None if format string
            cannot be determined.