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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 add_phrase(self, phrase: List[int]) -> None: """ Recursively adds a phrase to this trie node. :param phrase: A list of word IDs to add to this trie node. """

        if len(phrase) == 1:
            self.final_ids.add(phrase[0])
        else:
            next_word = phrase[0]
            if next_word not in self.children:
                self.children[next_word] = AvoidTrie()
            self.step(next_word).add_phrase(phrase[1:])