private RaftClientReply transferLeader(RaftGroup group, RaftPeer newLeader) throws Exception {
    try (RatisClient client = getRaftClient(group)) {
      return client
          .getRaftClient()
          .admin()
          .transferLeadership(newLeader != null ? newLeader.getId() : null, 10000);
    }
  }
NOTICE: transferLeader *does not guarantee* the leader be transferred to newLeader.
iotdb-core/consensus/src/main/java/org/apache/iotdb/consensus/ratis/RatisConsensus.java