code: func Sum512_256(data []byte) (sum256 [Size256]byte) {
  	d := digest{function: crypto.SHA512_256}
  	d.Reset()
  	d.Write(data)
  	sum := d.checkSum()
  	copy(sum256[:], sum[:Size256])
  	return
  }
docs: // Sum512_256 returns the Sum512/256 checksum of the data.