def differents_words_list(self, text):
    " select only the total of different words,\n        it's a set, return the set.\n        "
    return set(self.words_list(text))
select only the total of different words,
it's a set, return the set.
def differents_words_list(self, text):
    " select only the total of different words,\n        it's a set, return the set.\n        "
    return set(self.words_list(text))