如何在dlib中序列化random_forest？

Question

代码：

  random_forest_regression_trainer<dense_feature_extractor> trainer;
  random_forest_regression_function<dense_feature_extractor> model = trainer.train(data, labels);
  dlib::serialize(model, output);

但我只能找到

  serialize(const dense_feature_extractor& item, std::ostream& out)
  serialize(const random_forest_regression_function& item, std::ostream& out)

那么如何序列化random_forest_regression_function<dense_feature_extractor>？