code: def setUp(self):
      self.tokens = ["a", "b", "c"]
      self.vocab = Vocabulary(self.tokens)
      (a, b, c) = (self.vocab.tok2idx[tok] for tok in self.tokens[-3:])
      self.tok_seq = ["a", "a", "b", "c"]
      self.idx_seq = [a, a, b, c]
  
imports: import unittest
  from collections import defaultdict
  import numpy
  import numpy.testing
  from cornac.data import TextModality, ReviewModality
  from cornac.data.text import SPECIAL_TOKENS, DEFAULT_PRE_RULES, BaseTokenizer, Vocabulary, CountVectorizer, TfidfVectorizer
label_desc: Use image node_id 1 for calling the TestVocabulary obj's underlying member method code with example usage: obj.setUp() without return types