docs: def read_dictionary_file(dictionary_path):
      """Return all words in dictionary file as set."""
      try:
          return _user_dictionary_cache[dictionary_path]
      except KeyError:
          if dictionary_path and os.path.exists(dictionary_path):
              with open(dictionary_path, "rt") as dict_f:
                  words = set(re.findall(r"(\w[\w']*\w|\w)",
                                         " ".join(dict_f.read().splitlines())))
                  return words
  
          return set()