code: public Iterable<String> getMemberIds()
        throws ZooKeeperConnectionException, KeeperException, InterruptedException {
      return zkClient.get().getChildren(path, false)
          .stream()
          .filter(nodeNameFilter)
          .collect(Collectors.toList());
    }
docs: Returns the current list of group member ids by querying ZooKeeper synchronously.
  
  @return the ids of all the present members of this group
  @throws ZooKeeperConnectionException if there was a problem connecting to ZooKeeper
  @throws KeeperException if there was a problem reading this group's member ids
  @throws InterruptedException if this thread is interrupted listing the group members