class_docstr: tests Vocabulary Class
class_docstr_tok: ["tests","Vocabulary","Class"]
code: def test_update_empty_vocab(self):
      empty = Vocabulary(unk_cutoff=2)
      self.assertEqual(len(empty), 0)
      self.assertFalse(empty)
      self.assertIn(empty.unk_label, empty)
  
      empty.update(list("abcde"))
      self.assertIn(empty.unk_label, empty)
  
imports: import unittest
  from collections import Counter
  from timeit import timeit
  from nltk.lm import Vocabulary
label_desc: Use image node_id 10 for calling the NgramModelVocabularyTests obj's underlying member method code with example usage: obj.test_update_empty_vocab() without return types