code: def schedule(self, recipients=None, sender=None, priority=None):
          
          if priority is None:
              priority = self.priority
  
          self._message_model, self._dispatch_models = Message.create(
              self.get_alias(), self.get_context(), recipients=recipients, sender=sender, priority=priority
          )
          return self._message_model, self._dispatch_models
docs: Schedules message for a delivery.
          Puts message (and dispatches if any) data into DB.
  
          :param list|None recipients: recipient (or a list) or None.
              If `None` Dispatches should be created before send using `prepare_dispatches()`.
          :param User|None sender: Django User model heir instance
          :param int|None priority: number describing message priority
          :return: a tuple with message model and a list of dispatch models.
          :rtype: tuple