code: def size(self, index):
      sz = self.dataset.size(index)
      own_sz = self.label_len_fn(self.get_label(index))
      return sz, own_sz
  
file_path: fairseq/fairseq/data/add_target_dataset.py
imports: import torch
  from .None import BaseWrapperDataset, data_utils
  from fairseq.data.text_compressor import TextCompressor, TextCompressionLevel
label_desc: Use image node_id 4 for calling the AddTargetDataset obj's underlying member method code with example usage: obj.size(index) and returns: sz,  own_sz