Handle expander messages.

        :param data: expander message to parse
        :type data: string

        :returns: :py:class:`~alarmdecoder.messages.ExpanderMessage`

def _handle_expander_message(self, data):
        """
        Handle expander messages.

        :param data: expander message to parse
        :type data: string

        :returns: :py:class:`~alarmdecoder.messages.ExpanderMessage`
        """
        msg = ExpanderMessage(data)

        self._update_internal_states(msg)
        self.on_expander_message(message=msg)

        return msg