I check the pyotrch code and find in python code torch.jit.load return torch.jit.ScriptModule which is
inheritted from torch.nn.Module,so i can use torch.jit.ScriptModule like torch.nn.Module,
traced_script_module = torch.jit.load("model.pt")
traced_script_module.cuda()

but in C++  torch::jit::load return std::shared_ptr<lt;torch::jit::script::Module> which is a struct Module.https://github.com/pytorch/pytorch/blob/master/torch/csrc/jit/script/module.h 49