code: def size(self, index: int):
      if len(self.datasets) == 1:
          return self.datasets[0].size(index)
      return super().size(index)
  
imports: import logging
  import math
  from typing import List, Optional, NamedTuple
  import numpy
  import torch
  from fairseq.data import ConcatDataset, LanguagePairDataset, FileAudioDataset, data_utils
  from fairseq.data import FairseqDataset
label_desc: Use image node_id 5 for calling the MultiModalityDataset obj's underlying member method code with example usage: obj.size(index) and returns: super, self