class_docstr: Defines a vocabulary object that will be used to numericalize a field.
  
  Attributes:
      freqs: A collections.Counter object holding the frequencies of tokens
          in the data used to build the Vocab.
      stoi: A collections.defaultdict instance mapping token strings to
          numerical identifiers.
      itos: A list of token strings indexed by their numerical identifiers.
class_docstr_tok: ["Defines","a","vocabulary","object","that","will","be","used","to","numericalize","a","field",".","Attributes",":","freqs",":","A","collections.Counter","object","holding","the","frequencies","of","tokens","in","the","data","used","to","build","the","Vocab",".","stoi",":","A","collections.defaultdict","instance","mapping","token","strings","to","numerical","identifiers",".","itos",":","A","list","of","token","strings","indexed","by","their","numerical","identifiers","."]
code: def extend(self, v, sort=False):
      words = sorted(v.itos) if sort else v.itos
      for w in words:
          if w not in self.stoi:
              self.itos.append(w)
              self.stoi[w] = len(self.itos) - 1
  
imports: from __future__ import unicode_literals
  import array
  from collections import defaultdict
  import io
  import logging
  import os
  import zipfile
  import six
  from six.moves.urllib.request import urlretrieve
  import torch
  from tqdm import tqdm
  import tarfile
  from .utils import reporthook
label_desc: Use image node_id 4 for calling the Vocab obj's underlying member method code with example usage: obj.extend(v, sort) without return types