code: func (db *DB) ZMclear(keys ...[]byte) (int64, error) {
  	t := db.zsetBatch
  	t.Lock()
  	defer t.Unlock()
  
  	for _, key := range keys {
  		if _, err := db.zRemRange(t, key, MinScore, MaxScore, 0, -1); err != nil {
  			return 0, err
  		}
  	}
  
  	err := t.Commit()
  
  	return int64(len(keys)), err
  }
docs: // ZMclear clears multi zsets.