code: def file_generator(self):
      batch = []
      for i, file in enumerate(os.listdir(self.inputdir)):
          if self.subset_list is not None and i not in self.subset_list:
              continue
          batch.append(self._vqa_file_split(file))
          if len(batch) == self.batch:
              temp = batch
              batch = []
              yield list(map(list, zip(*temp)))
  
      for i in range(1):
          yield list(map(list, zip(*batch)))
  
file_path: transformers/examples/research_projects/lxmert/extracting_data.py
imports: import getopt
  import json
  import os
  import sys
  from collections import OrderedDict
  import datasets
  import numpy
  import torch
  from modeling_frcnn import GeneralizedRCNN
  from processing_image import Preprocess
  from utils import Config
label_desc: Use image node_id 3 for calling the Extract obj's underlying member method code with example usage: obj.file_generator() without return types