docs: public void addVirtualPartitionNode(Integer originalId, Integer virtualId, StreamPartitioner<?> partitioner) {
  
  		if (virtualPartitionNodes.containsKey(virtualId)) {
  			throw new IllegalStateException("Already has virtual partition node with id " + virtualId);
  		}
  
  		virtualPartitionNodes.put(virtualId,
  				new Tuple2<Integer, StreamPartitioner<?>>(originalId, partitioner));
  	}