code: def sizes(self):
      # dataset.sizes can be a dynamically computed sizes:
      return self.dataset.sizes
  
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 4 for calling the LangPairMaskDataset obj's underlying member method code with example usage: obj.sizes() and returns: self