code: def testFilterKeepTokens_unseenToken(self):
      # do provide keep_tokens argument with unseen tokens, filter_extremes functionality is unchanged
      d = Dictionary(self.texts)
      d.filter_extremes(
          no_below=3, no_above=1.0, keep_tokens=["unknown_token"]
      )
      expected = {"graph", "trees", "system", "user"}
      self.assertEqual(set(d.token2id.keys()), 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 11 for calling the TestDictionary obj's underlying member method code with example usage: obj.testFilterKeepTokens_unseenToken() without return types