code: def test_increment(self):
      # make sure that we can still mutate cfd normally
      text = "cow cat mouse cat tiger"
      cfd = ConditionalFreqDist()
  
      # create cfd with word length as condition
      for word in tokenize.word_tokenize(text):
          condition = len(word)
          cfd[condition][word] += 1
  
      self.assertEqual(cfd.conditions(), [3, 5])
  
      # incrementing previously unseen key is still possible
      cfd[2]["hi"] += 1
      self.assertCountEqual(
          cfd.conditions(), [3, 5, 2]
      )  # new condition added
      self.assertEqual(cfd[2]["hi"], 1)
  
file_path: nltk/nltk/test/unit/test_cfd_mutation.py
imports: import unittest
  import pytest
  from nltk import ConditionalFreqDist, tokenize
label_desc: Use image node_id 3 for calling the TestEmptyCondFreq obj's underlying member method code with example usage: obj.test_increment() without return types