code: func (db *DB) ZDump(key []byte) ([]byte, error) {
  	v, err := db.ZRangeByScore(key, MinScore, MaxScore, 0, -1)
  	if err != nil {
  		return nil, err
  	} else if len(v) == 0 {
  		return nil, err
  	}
  
  	o := make(rdb.ZSet, len(v))
  	for i := 0; i < len(v); i++ {
  		o[i].Member = v[i].Member
  		o[i].Score = float64(v[i].Score)
  	}
  
  	return rdb.Dump(o)
  }
docs: // ZDump dumps the zset value of key