code: func (db *DB) Persist(key []byte) (int64, error) {
  	if err := checkKeySize(key); err != nil {
  		return 0, err
  	}
  
  	t := db.kvBatch
  	t.Lock()
  	defer t.Unlock()
  	n, err := db.rmExpire(t, KVType, key)
  	if err != nil {
  		return 0, err
  	}
  
  	err = t.Commit()
  	return n, err
  }
docs: // Persist removes the TTL of the data.