func AddLabelToSelector(selector *LabelSelector, labelKey, labelValue string) *LabelSelector {
	if labelKey == "" {
		return selector
	}
	if selector.MatchLabels == nil {
		selector.MatchLabels = make(map[string]string)
	}
	selector.MatchLabels[labelKey] = labelValue
	return selector
}
AddLabelToSelector returns a selector with the given key and value added to the given selector's MatchLabels.
package v1
func CloneSelectorAndAddLabel(selector *LabelSelector, labelKey, labelValue string) *LabelSelector {
	if labelKey == "" {
		return selector
	}
	newSelector := selector.DeepCopy()
	if newSelector.MatchLabels == nil {
		newSelector.MatchLabels = make(map[string]string)
	}
	newSelector.MatchLabels[labelKey] = labelValue
	return newSelector
}