Extending torchscript a custom class with member variables in torch c++

How can I create a custom class with member variables in c++ and use the variables in python?

Now i construct this cpp code.

class Loader : public torch::CustomClassHolder{
 public:
  Loader(const std::string& path);
  std::vector<int64_t> get_config(const std::string& filename);
  std::vector<int64_t> meta_json;
};

# ------------------

TORCH_LIBRARY(name, ops) {
     ops.class_<Loader>("Loader")
        .def(torch::init<const std::string>())
        .def("get_config", &Loader::get_config);
}

but i can’t use “Loader().meta_json” in python

model = torch.classes.name.Loader("xxx.path")
print(model.meta_json) # error with "meta_json" not found.

So, how can i register the class member in python?

Thanks for your help~