func InvertStages(stages []audit.Stage) []audit.Stage {
	s := ConvertStagesToStrings(stages)
	a := AllStages()
	a.Delete(s...)
	return ConvertStringSetToStages(a)
}

// ConvertStagesToStrings converts an array of stages to a string array
func ConvertStagesToStrings(stages []audit.Stage) []string {
	s := make([]string, len(stages))
	for i, stage := range stages {
		s[i] = string(stage)