Graph.WhileSubgraphBuilder

 WhileSubgraphBuilder bodyGraphBuilder = new WhileSubgraphBuilder() {
   @Override
   public void buildSubgraph(Graph bodyGraph, Output<?>[] bodyInputs, Output<?>[] bodyOutputs) { // build
     body subgraph
   }
 };
 

 WhileSubgraphBuilder bodyGraphBuilder = (bodyGraph, bodyInputs, bodyOutputs) -> { //
   build body subgraph
 };