:param ppSeqNo:
        :return: True if ppSeqNo is less than or equal to last stable
        checkpoint, false otherwise

def is_pp_seq_no_stable(self, msg: Checkpoint):
        """
        :param ppSeqNo:
        :return: True if ppSeqNo is less than or equal to last stable
        checkpoint, false otherwise
        """
        pp_seq_no = msg.seqNoEnd
        ck = self.firstCheckPoint
        if ck:
            _, ckState = ck
            return ckState.isStable and ckState.seqNo >= pp_seq_no
        else:
            return False