Shuffles the Stack.

        .. note::
            Shuffling large numbers of cards (100,000+) may take a while.

        :arg int times:
            The number of times to shuffle.

def shuffle(self, times=1):
        """
        Shuffles the Stack.

        .. note::
            Shuffling large numbers of cards (100,000+) may take a while.

        :arg int times:
            The number of times to shuffle.

        """
        for _ in xrange(times):
            random.shuffle(self.cards)