private boolean termPredicate(HashMap<Long, Vote> votes, Vote vote) { //
        SyncedLearnerTracker voteSet = new SyncedLearnerTracker();
        voteSet.addQuorumVerifier(self.getQuorumVerifier());//
        if (self.getLastSeenQuorumVerifier() != null
                && self.getLastSeenQuorumVerifier().getVersion() > self //LastSeenQuorumVerifierversionversion(member)
                        .getQuorumVerifier().getVersion()) {
            voteSet.addQuorumVerifier(self.getLastSeenQuorumVerifier());//LastSeenQuorumVerifier
        }

        /*
         * First make the views consistent. Sometimes peers will have different
         * zxids for a server depending on timing.
         */
        for (Map.Entry<Long, Vote> entry : votes.entrySet()) {//
            if (vote.equals(entry.getValue())) {//voter
                voteSet.addAck(entry.getKey());
            }
        }

        return voteSet.hasAllQuorums();//
    }

Why does zk need two voting devices to determine the end of the vote?

    //last committed quorum verifier
    public QuorumVerifier quorumVerifier;
    
    //last proposed quorum verifier ()
    public QuorumVerifier lastSeenQuorumVerifier = null; //