// the key of the function definition name (to be retrieved during function
  // instantiation).
  virtual Status AddFunctionDefWithStackTraces(
      const FunctionDef& fdef, const StackTracesMap& stack_traces) = 0;

  // Find and return a added function by its name.
  virtual const FunctionDef* FindFunctionDef(const string& name) const = 0;

  // Find and return a function record added by its name.

  }

  // Dump the op creation stacktraces for debugging purpose.
  DEBUG_DATA_DUMPER()->DumpOpCreationStackTraces(
      fn_name, kDebugGroupOpStacktrace, "initial", &fn_body->graph);

  tensorflow::StackTracesMap stack_traces;
  for (const Node* n : fn_body->graph.nodes()) {
    stack_traces[n->name()] = n->GetStackTrace();
  }

  TF_Function* tf_function = new TF_Function();

  TF_GraphCopyFunction(host_graph_, func_, grad_func, s_);

  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);

  TF_DeleteFunction(grad_func);

  const StackTracesMap* func_stack_traces;
  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_);