code: def test_filter_most_frequent(self):
      d = Dictionary(self.texts)
      d.filter_n_most_frequent(4)
      expected = {0: 2, 1: 2, 2: 2, 3: 2, 4: 2, 5: 2, 6: 2, 7: 2}
      self.assertEqual(d.dfs, expected)
  
imports: from collections.abc import Mapping
  from itertools import chain
  import logging
  import unittest
  import codecs
  import os
  import os.path
  import scipy
  import gensim
  from gensim.corpora import Dictionary
  from gensim.utils import to_utf8
  from gensim.test.utils import get_tmpfile, common_texts
label_desc: Use image node_id 13 for calling the TestDictionary obj's underlying member method code with example usage: obj.test_filter_most_frequent() without return types