docs: private long computeHeartbeatTime() {
      int quorumIndex = getQuorumIndex();
      if (quorumIndex >= 0) {
        return raft.getCluster().getActiveMemberStates((m1, m2) -> Long.compare(m2.getHeartbeatTime(), m1.getHeartbeatTime())).get(quorumIndex).getHeartbeatTime();
      }
      return System.currentTimeMillis();
    }