docs: def mget(self, args):
          """
          mget wrapper that batches keys per shard and execute as few
          mgets as necessary to fetch the keys from all the shards involved.
  
          This method should be invoked on a TwemRedis instance as if it
          were being invoked directly on a StrictRedis instance.
          """
          key_map = collections.defaultdict(list)
          results = {}
          for key in args:
              shard_num = self.get_shard_num_by_key(key)
              key_map[shard_num].append(key)
  
          # TODO: parallelize
          for shard_num in key_map.keys():
              shard = self.get_shard_by_num(shard_num)
              results[shard_num] = shard.mget(key_map[shard_num])
          return results