// [Optional]
  // Destroy function for optimizer. If Create function is provided, destroy
  // function is must.
  void (*destroy_func)(void*);
} TP_Optimizer;

#define TP_OPTIMIZER_STRUCT_SIZE TF_OFFSET_OF_END(TP_Optimizer, destroy_func)

typedef struct TP_OptimizerRegistrationParams {
  size_t struct_size;
  void* ext;  // reserved for future use

  // Graph C API version.

};
using OwnedTFBuffer = std::unique_ptr<TF_Buffer, TFBufferDeleter>;

class CGraphOptimizer : public CustomGraphOptimizer {
 public:
  explicit CGraphOptimizer(TP_Optimizer optimizer, const char* device_type)
      : optimizer_(optimizer), device_type_(device_type) {
    if (optimizer.create_func != nullptr) {
      c_optimizer_ = (*optimizer_.create_func)();
    } else {

  VALIDATE_MEMBER(TP_OptimizerRegistrationParams, params, device_type);
  return absl::OkStatus();
}

absl::Status ValidateTPOptimizer(const TP_Optimizer& optimizer) {
  VALIDATE_STRUCT_SIZE(TP_Optimizer, optimizer, TP_OPTIMIZER_STRUCT_SIZE);
  VALIDATE_MEMBER(TP_Optimizer, optimizer, optimize_func);
  return absl::OkStatus();
}

absl::Status ValidateTPOptimizerConfigs(const TP_OptimizerConfigs& configs) {

  };

  tensorflow::Status status = InitGraphPlugin(plugin_init);
  ASSERT_EQ(status.code(), tensorflow::error::FAILED_PRECONDITION);
  ASSERT_EQ(status.message(),
            "'optimize_func' field in TP_Optimizer must be set.");
}

TEST(TF_GrapplerItem, NodesToPreserve) {
  GrapplerItem item;
  item.fetch = std::vector<string>{"Conv", "BiasAdd"};
  std::unordered_set<string> nodes_preserved = item.NodesToPreserve();