code: def add_valid(self, data, name):
          
          if not isinstance(data, Dataset):
              raise TypeError('Validation data should be Dataset instance, met {}'
                              .format(type(data).__name__))
          if data._predictor is not self.__init_predictor:
              raise LightGBMError("Add validation data failed, "
                                  "you should use same predictor for these data")
          _safe_call(_LIB.LGBM_BoosterAddValidData(
              self.handle,
              data.construct().handle))
          self.valid_sets.append(data)
          self.name_valid_sets.append(name)
          self.__num_dataset += 1
          self.__inner_predict_buffer.append(None)
          self.__is_predicted_cur_iter.append(False)
          return self
docs: Add validation data.
  
          Parameters
          ----------
          data : Dataset
              Validation data.
          name : string
              Name of validation data.
  
          Returns
          -------
          self : Booster
              Booster with set validation data.