docs: public static BabySitter nonblockingFactory(ZooKeeper zk, String dir,
                                                  Callback cb, ExecutorService es)
          throws InterruptedException, ExecutionException
      {
          BabySitter bs = new BabySitter(zk, dir, cb, es);
          bs.m_es.submit(bs.m_eventHandler);
          return bs;
      }