code: def changePlanParticipation(self, plan, take_part=True):
          
          data = {
              "event_reminder_id": plan.uid,
              "guest_state": "GOING" if take_part else "DECLINED",
              "acontext": ACONTEXT,
          }
          j = self._post(
              self.req_url.PLAN_PARTICIPATION, data, fix_request=True, as_json=True
          )
docs: Changes participation in a plan
  
          :param plan: Plan to take part in or not
          :param take_part: Whether to take part in the plan
          :raises: FBchatException if request failed