code: def retain(self, res, b):
      return retain_types(res, b[0] if is_listy(b) else b)
  
imports: from __future__ import annotations
  from ..torch_basics import *
  from torch.utils.data.dataloader import _MultiProcessingDataLoaderIter, _SingleProcessDataLoaderIter, _DatasetKind
label_desc: Use image node_id 15 for calling the DataLoader obj's underlying member method code with example usage: obj.retain(res, b) and returns: retain_types