code: func (w *MultiLevelSkipListWriter) WriteSkip(output IndexOutput) (int64, error) {
  	skipPointer := output.FilePointer()
  	if len(w.skipBuffer) == 0 {
  		return skipPointer, nil
  	}
  
  	for level := w.numberOfSkipLevels - 1; level > 0; level-- {
  		if length := w.skipBuffer[level].FilePointer(); length > 0 {
  			err := output.WriteVLong(length)
  			if err != nil {
  				return 0, err
  			}
  			err = w.skipBuffer[level].WriteTo(output)
  			if err != nil {
  				return 0, err
  			}
  		}
  	}
  	return skipPointer, w.skipBuffer[0].WriteTo(output)
  }
docs: /* Writes the buffered skip lists to the given output. */