// MetricDescriptor - represents a metric descriptor.
type MetricDescriptor struct {
	Name           MetricName
	Type           MetricType
	Help           string
	VariableLabels []string

	// managed values follow:
	labelSet map[string]struct{}
}

func (md *MetricDescriptor) getLabelSet() map[string]struct{} {
	if md.labelSet != nil {
		return md.labelSet
	}