code: def rollback_one_iter(self):
          
          _safe_call(_LIB.LGBM_BoosterRollbackOneIter(
              self.handle))
          self.__is_predicted_cur_iter = [False for _ in range_(self.__num_dataset)]
          return self
docs: Rollback one iteration.
  
          Returns
          -------
          self : Booster
              Booster with rolled back one iteration.