code: def __len__(self):
      return len(self.data)
  
imports: import re
  import os
  import sys
  import random
  import string
  import logging
  import argparse
  from shutil import copyfile
  from datetime import datetime
  from collections import Counter
  import torch
  import msgpack
  import pandas
  from drqa.model import DocReaderModel
  from drqa.utils import str2bool
label_desc: Use image node_id 2 for calling the BatchGen obj's underlying member method code with example usage: obj.__len__() and returns: len