code: def _get_single_call_funcs(self):
      return MMFConcatDataset._SINGLE_CALL_FUNCS
  
file_path: mmf/mmf/datasets/concat_dataset.py
imports: import functools
  import types
  from torch.utils.data import ConcatDataset
label_desc: Use image node_id 3 for calling the MMFConcatDataset obj's underlying member method code with example usage: obj._get_single_call_funcs() and returns: MMFConcatDataset