SortedSet（有序集合）

.. toctree::
   :maxdepth: 2

   zadd
   zcard
   zcount
   zincrby
   zrange
   zrangebyscore
   zrank
   zrem
   zremrangebyrank
   zremrangebyscore
   zrevrange
   zrevrangebyscore
   zrevrank
   zscore
   zunionstore
   zinterstore
   zscan