code: func NewMultiLevelSkipListWriter(spi MultiLevelSkipListWriterSPI,
  	skipInterval, skipMultiplier, maxSkipLevels, df int) *MultiLevelSkipListWriter {
  
  	numberOfSkipLevels := 1
  	// calculate the maximum number of skip levels for this document frequency
  	if df > skipInterval {
  		numberOfSkipLevels = 1 + util.Log(int64(df/skipInterval), skipMultiplier)
  	}
  	// make sure it does not exceed maxSkipLevels
  	if numberOfSkipLevels > maxSkipLevels {
  		numberOfSkipLevels = maxSkipLevels
  	}
  	return &MultiLevelSkipListWriter{
  		spi:                spi,
  		skipInterval:       skipInterval,
  		skipMultiplier:     skipMultiplier,
  		numberOfSkipLevels: numberOfSkipLevels,
  	}
  }
docs: /* Creates a MultiLevelSkipListWriter. */