code: func parseDeltaSeconds(v string) (DeltaSeconds, error) {
  	n, err := strconv.ParseUint(v, 10, 32)
  	if err != nil {
  		if numError, ok := err.(*strconv.NumError); ok {
  			if numError.Err == strconv.ErrRange {
  				return DeltaSeconds(math.MaxInt32), nil
  			}
  		}
  		return DeltaSeconds(-1), err
  	} else {
  		if n > math.MaxInt32 {
  			return DeltaSeconds(math.MaxInt32), nil
  		} else {
  			return DeltaSeconds(n), nil
  		}
  	}
  }
docs: // Parser for delta-seconds, a uint31, more or less:
  // http://tools.ietf.org/html/rfc7234#section-1.2.1