code: def __len__(self):
      return self._size
  
imports: import argparse
  import numpy
  import operator
  import os
  import sys
  from collections import Counter
  import tensorflow
  from tensorpack import *
  from tensorpack.tfutils import optimizer, summary
  from tensorpack.tfutils.gradproc import GlobalNormClip
label_desc: Use image node_id 2 for calling the CharRNNData obj's underlying member method code with example usage: obj.__len__() and returns: self