docs: def clean_list_of_twitter_list(list_of_twitter_lists,
                                 sent_tokenize, _treebank_word_tokenize,
                                 tagger, lemmatizer, lemmatize, stopset,
                                 first_cap_re, all_cap_re, digits_punctuation_whitespace_re,
                                 pos_set):
      """
      Extracts the sets of keywords for each Twitter list.
  
      Inputs: - list_of_twitter_lists: A python list of Twitter lists in json format.
              - lemmatizing: A string containing one of the following: "porter", "snowball" or "wordnet".
  
      Output: - list_of_keyword_sets: A list of sets of keywords (i.e. not a bag-of-words) in python set format.
              - list_of_lemma_to_keywordbags: List of python dicts that map stems/lemmas to original topic keywords.
      """
      list_of_keyword_sets = list()
      append_keyword_set = list_of_keyword_sets.append
  
      list_of_lemma_to_keywordbags = list()
      append_lemma_to_keywordbag = list_of_lemma_to_keywordbags.append
  
      if list_of_twitter_lists is not None:
          for twitter_list in list_of_twitter_lists:
              if twitter_list is not None:
                  keyword_set, lemma_to_keywordbag = clean_twitter_list(twitter_list,
                                                                        sent_tokenize, _treebank_word_tokenize,
                                                                        tagger, lemmatizer, lemmatize, stopset,
                                                                        first_cap_re, all_cap_re, digits_punctuation_whitespace_re,
                                                                        pos_set)
                  append_keyword_set(keyword_set)
                  append_lemma_to_keywordbag(lemma_to_keywordbag)
  
      return list_of_keyword_sets, list_of_lemma_to_keywordbags