code: def vocab_size(self):
      return len(self.w2i)
  
imports: import io
  import json
  import os
  import pickle
  from collections import Counter, OrderedDict
  from collections import defaultdict
  import numpy
  import torch
  import torch.nn
  from nltk.tokenize import sent_tokenize, word_tokenize
  from torch.utils.data import Dataset
  from torchvision import transforms, models, datasets
label_desc: Use image node_id 4 for calling the CUBSentences obj's underlying member method code with example usage: obj.vocab_size() and returns: len