code: func (t *Taint) ToString() string {
  	if len(t.Value) == 0 {
  		return fmt.Sprintf("%v:%v", t.Key, t.Effect)
  	}
  	return fmt.Sprintf("%v=%v:%v", t.Key, t.Value, t.Effect)
  }
docs: // taint.ToString() converts taint struct to string in format key=value:effect or key:effect.