code: private ClusterHeartbeat createCluster(String name)
    {
      if (name.equals("")) {
        throw new IllegalArgumentException();
      }
      
      return _root.createCluster(name);
    }
docs: /*
  @Override
  public void serverSelf(String address,
  int port,
  String clusterId,
  String displayName)
  {
  Objects.requireNonNull(address);
  Objects.requireNonNull(clusterId);
  
  ClusterHeartbeat cluster = createCluster(clusterId);
  }