code: def set_completed(self, *, completition_date=None):
          
          self.__status = Flag.Complete
          completition_date = completition_date or dt.datetime.now()
          if completition_date.tzinfo is None:
              completition_date = self.protocol.timezone.localize(completition_date)
          self.__completed = completition_date
          self._track_changes()
docs: Sets this message flag as completed
          :param completition_date: the datetime this followUp was completed