code: func (l *WAL) Delete(keys [][]byte) (int, error) {
  	if len(keys) == 0 {
  		return 0, nil
  	}
  	entry := &DeleteWALEntry{
  		Keys: keys,
  	}
  
  	id, err := l.writeToLog(entry)
  	if err != nil {
  		return -1, err
  	}
  	return id, nil
  }
docs: // Delete deletes the given keys, returning the segment ID for the operation.