rule/rule.go
func (r *Rule) PrivateAttrKeys() []string {
	keys := make([]string, 0, len(r.private))
	for k := range r.private {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}
func (r *Rule) PrivateAttrKeys() []string {
	keys := make([]string, 0, len(r.private))
	for k := range r.private {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}
// PrivateAttrKeys returns a sorted list of private attribute names.