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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 get_top_level_forum_url(self):
 """ Returns the parent forum from which forums are marked as read. """

        return (
            reverse('forum:index') if self.top_level_forum is None else
            reverse(
                'forum:forum',
                kwargs={'slug': self.top_level_forum.slug, 'pk': self.kwargs['pk']},
            )
        )