code: func tokenConstraintTime(value ast.Value, constraints *tokenConstraints) (err error) {
  	var time ast.Number
  	var ok bool
  	if time, ok = value.(ast.Number); !ok {
  		err = fmt.Errorf("token time constraint: must be a number")
  		return
  	}
  	var timeFloat float64
  	if timeFloat, err = strconv.ParseFloat(string(time), 64); err != nil {
  		err = fmt.Errorf("token time constraint: %v", err)
  		return
  	}
  	if timeFloat < 0 {
  		err = fmt.Errorf("token time constraint: must not be negative")
  		return
  	}
  	constraints.time = int64(timeFloat)
  	return
  }
docs: // tokenConstraintTime handles the `time` constraint.