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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _is_catch_phrase_valid(self, catch_phrase):
 """ Validates a french catch phrase. :param catch_phrase: The catch phrase to validate. """

        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