code: def _ch_dev(arg_params, aux_params, ctx):
      
      new_args = dict()
      new_auxs = dict()
      for k, v in arg_params.items():
          new_args[k] = v.as_in_context(ctx)
      for k, v in aux_params.items():
          new_auxs[k] = v.as_in_context(ctx)
      return new_args, new_auxs
docs: Changes device of given mxnet arguments
      :param arg_params: arguments
      :param aux_params: auxiliary parameters
      :param ctx: new device context
      :return: arguments and auxiliary parameters on new device