code: func Version(h string) int {
  	if h == "" {
  		return -1
  	}
  	if h[0] != 'v' {
  		return -1
  	}
  	if spos := strings.IndexRune(h[1:], '_'); spos >= 0 {
  		n, e := strconv.Atoi(h[1 : spos+1])
  		if e != nil {
  			return -1
  		}
  		return n
  	}
  	return -1
  }
docs: // Version returns the version of the supplied hash as an integer
  // or -1 on failure