code: func (kf *KeyFormat) ScanBytes(key []byte) [][]byte {
  	segments := make([][]byte, len(kf.layout))
  	n := kf.prefix.Length()
  	for i, l := range kf.layout {
  		if l == 0 {
  			// Must be final variadic segment
  			segments[i] = key[n:]
  			return segments
  		}
  		n += l
  		if n > len(key) {
  			return segments[:i]
  		}
  		segments[i] = key[n-l : n]
  	}
  	return segments
  }
docs: // Reads out the bytes associated with each segment of the key format from key.