const StackTracesMap* grad_stack_traces;

  {
    mutex_lock l(host_graph_->mu);
    auto flib_def = host_graph_->graph.flib_def();
    func_stack_traces = flib_def.GetStackTraces(func_name_);
    grad_stack_traces = flib_def.GetStackTraces("MyGrad");
  }

  // Verify that stack traces of func is copied to graph function library.
  ASSERT_NE(func_stack_traces, nullptr);
  EXPECT_EQ(func_stack_traces->size(), 4);