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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 save(self, *args, **kwargs):
 """ Store a string representation of content_object as target and actor name for fast retrieval and sorting. """

        if not self.target:
            self.target = str(self.content_object)
        if not self.actor_name:
            self.actor_name = str(self.actor)
        super(Activity, self).save()