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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 lemma_lists(self):
 """Lemma lists. Ambiguous cases are separate list elements. """

        if not self.is_tagged(ANALYSIS):
            self.tag_analysis()
        return [[an[LEMMA] for an in word[ANALYSIS]] for word in self[WORDS]]