private @NotNull Graph<Node> toGraph(Map<Node, Set<Node>> resultGraph) {
    return new Graph<Node>() {
      @Override
      public @NotNull Collection<Node> getNodes() {
        return resultGraph.keySet();
      }

      @Override
      public @NotNull Iterator<Node> getIn(Node node) {
        return Collections.emptyIterator();
      }

      @Override
      public @NotNull Iterator<Node> getOut(Node node) {
        Set<Node> nodes = resultGraph.get(node);
        return nodes != null ? nodes.iterator() : Collections.emptyIterator();
      }
    };
  }
private @NotNull Graph<Node> toGraph(Map<Node, Set<Node>> resultGraph)