code: def _is_catch_phrase_valid(self, catch_phrase):
          
          for word in self.words_which_should_not_appear_twice:
              # Fastest way to check if a piece of word does not appear twice.
              begin_pos = catch_phrase.find(word)
              end_pos = catch_phrase.find(word, begin_pos + 1)
  
              if begin_pos != -1 and begin_pos != end_pos:
                  return False
  
          return True
docs: Validates a french catch phrase.
  
          :param catch_phrase: The catch phrase to validate.