TF_SessionOptions* opt = TF_NewSessionOptions();
  TF_Status* s = TF_NewStatus();
  const char* tags[] = {tensorflow::kSavedModelTagServe};
  TF_Graph* graph = TF_NewGraph();
  // NULL run_options and meta_graph_def should work.
  TF_Session* session = TF_LoadSessionFromSavedModel(
      opt, nullptr, saved_model_dir.c_str(), tags, 1, graph, nullptr, s);
  EXPECT_EQ(TF_OK, TF_GetCode(s)) << TF_Message(s);

  /// `paths` would set `status` to `TF_OK`.
  ///
  /// Caller guarantees that:
  ///   * `paths` has exactly `num_files` entries.
  ///   * `statuses` is either null or an array of `num_files` non-null elements
  ///     of type `TF_Status*`.
  ///
  /// If `statuses` is not null, plugins must fill each element with detailed
  /// status for each file, as if calling `path_exists` on each one. Core

  DefineFunction("MyGrad1", &grad_func1);
  DefineFunction("MyGrad2", &grad_func2);

  // func cannot be null
  TF_GraphCopyFunction(host_graph_, nullptr, func_, s_);
  EXPECT_EQ(TF_INVALID_ARGUMENT, TF_GetCode(s_));
  EXPECT_EQ(string("'func' argument to TF_GraphCopyFunction cannot be null"),
            string(TF_Message(s_)));

  // Cannot change gradient

//
// Any NULL and non-NULL value combinations for (`run_options`,
// `run_metadata`) are valid.
//
//    - `run_options` may be NULL, in which case it will be ignored; or
//      non-NULL, in which case it must point to a `TF_Buffer` containing the
//      serialized representation of a `RunOptions` protocol buffer.
//    - `run_metadata` may be NULL, in which case it will be ignored; or