Unsends a message (removes for everyone)

        :param mid: :ref:`Message ID <intro_message_ids>` of the message to unsend

def unsend(self, mid):
        """
        Unsends a message (removes for everyone)

        :param mid: :ref:`Message ID <intro_message_ids>` of the message to unsend
        """
        data = {"message_id": mid}
        r = self._post(self.req_url.UNSEND, data)
        r.raise_for_status()