Scope root = Scope::NewRootScope().ExitOnError();

  Output a = ops::Const(root.WithOpName("a"), Input::Initializer(0.0));
  Output enter =
      ops::internal::Enter(root.WithOpName("enter"), a, "only_frame");
  Output exit = ops::internal::Exit(root.WithOpName("exit"), enter);
  Output b = ops::Add(root.WithOpName("b"), a, exit);

  FixupSourceAndSinkEdges(root.graph());

  GraphCycles cycles;