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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 keys(self, args):
 """ keys wrapper that queries every shard. This is an expensive operation. This method should be invoked on a TwemRedis instance as if it were being invoked directly on a StrictRedis instance. """

        results = {}
        # TODO: parallelize
        for shard_num in range(0, self.num_shards()):
            shard = self.get_shard_by_num(shard_num)
            results[shard_num] = shard.keys(args)
        return results