code: def on_fold_end(self, validation_index, *args, **kwargs):
      self.T.rep.iloc[validation_index] += self.T.fold
  
imports: from hyperparameter_hunter.data.data_core import BaseDataChunk
  from copy import deepcopy
label_desc: Use image node_id 6 for calling the OOFTargetChunk obj's underlying member method code with example usage: obj.on_fold_end(validation_index) without return types