code: def _handle_expander_message(self, data):
          
          msg = ExpanderMessage(data)
  
          self._update_internal_states(msg)
          self.on_expander_message(message=msg)
  
          return msg
docs: Handle expander messages.
  
          :param data: expander message to parse
          :type data: string
  
          :returns: :py:class:`~alarmdecoder.messages.ExpanderMessage`