code: def setUp(self):
      self.docs = ["this is a sample", "this is another example"]
  
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 TestTfidfVectorizer obj's underlying member method code with example usage: obj.setUp() without return types