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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 sort(self, ranks=None):
 """ Sorts the stack, either by poker ranks, or big two ranks. :arg dict ranks: The rank dict to reference for sorting. If ``None``, it will default to ``DEFAULT_RANKS``. :returns: The sorted cards. """

        ranks = ranks or self.ranks
        self.cards = sort_cards(self.cards, ranks)