class_docstr: tests Vocabulary Class
class_docstr_tok: ["tests","Vocabulary","Class"]
code: def test_truthiness(self):
      self.assertTrue(self.vocab)
  
imports: import unittest
  from collections import Counter
  from timeit import timeit
  from nltk.lm import Vocabulary
label_desc: Use image node_id 2 for calling the NgramModelVocabularyTests obj's underlying member method code with example usage: obj.test_truthiness() without return types