<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def reactToMessage(self, message_id, reaction):
 """ Reacts to a message, or removes reaction :param message_id: :ref:`Message ID <intro_message_ids>` to react to :param reaction: Reaction emoji to use, if None removes reaction :type reaction: models.MessageReaction or None :raises: FBchatException if request failed """

        data = {
            "action": "ADD_REACTION" if reaction else "REMOVE_REACTION",
            "client_mutation_id": "1",
            "actor_id": self._uid,
            "message_id": str(message_id),
            "reaction": reaction.value if reaction else None,
        }
        data = {"doc_id": 1491398900900362, "variables": json.dumps({"data": data})}
        self._post(self.req_url.MESSAGE_REACTION, data, fix_request=True, as_json=True)