code: func TraceIDFromHex(h string) (t TraceID, err error) {
  	if len(h) > 16 {
  		if t.High, err = strconv.ParseUint(h[0:len(h)-16], 16, 64); err != nil {
  			return
  		}
  		t.Low, err = strconv.ParseUint(h[len(h)-16:], 16, 64)
  		return
  	}
  	t.Low, err = strconv.ParseUint(h, 16, 64)
  	return
  }
docs: // TraceIDFromHex returns the TraceID from a hex string.