code: def set_params(self, arg_params, aux_params, allow_extra=False):
          
          for exec_ in self.execs:
              exec_.copy_params_from(arg_params, aux_params, allow_extra_params=allow_extra)
docs: Assign, i.e. copy parameters to all the executors.
  
          Parameters
          ----------
          arg_params : dict
              A dictionary of name to `NDArray` parameter mapping.
          aux_params : dict
              A dictionary of name to `NDArray` auxiliary variable mapping.
          allow_extra : boolean, optional
              Whether allow extra parameters that are not needed by symbol.
              If this is True, no error will be thrown when arg_params or aux_params
              contain extra parameters that is not needed by the executor.