code: def save_checkpoint(prefix, epoch, arg_params, aux_params):
      """Checkpoint the model data into file.
      :param prefix: Prefix of model name.
      :param epoch: The epoch number of the model.
      :param arg_params: dict of str to NDArray
          Model parameter, dict of name to NDArray of net's weights.
      :param aux_params: dict of str to NDArray
          Model parameter, dict of name to NDArray of net's auxiliary states.
      :return: None
      prefix-epoch.params will be saved for parameters.
      """
      save_dict = {("arg:%s" % k): v for k, v in arg_params.items()}
      save_dict.update(
          {("aux:%s" % k): v for k, v in aux_params.items()}
      )
      param_name = "%s-%04d.params" % (prefix, epoch)
      mx.nd.save(param_name, save_dict)
  
label_desc: Use image node_id 1 for calling a global function with example usage: save_checkpoint(prefix, epoch, arg_params, aux_params) without return types