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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 named_entities(self):
 """The elements of ``named_entities`` layer."""

        if not self.is_tagged(NAMED_ENTITIES):
            self.tag_named_entities()
        phrases = self.split_by(NAMED_ENTITIES)
        return [' '.join(phrase.lemmas) for phrase in phrases]