// derived from an EndpointSlice.
func endpointsControllerKey(endpointSlice *discovery.EndpointSlice) (string, error) {
	if endpointSlice == nil {
		return "", fmt.Errorf("nil EndpointSlice passed to serviceControllerKey()")
	}
	serviceName, ok := endpointSlice.Labels[discovery.LabelServiceName]
	if !ok || serviceName == "" {
		return "", fmt.Errorf("EndpointSlice missing %s label", discovery.LabelServiceName)
	}

// the provided EndpointSlice.
func (c *Controller) queueServiceForEndpointSlice(endpointSlice *discovery.EndpointSlice) {
	key, err := endpointslicerec.ServiceControllerKey(endpointSlice)
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("Couldn't get key for EndpointSlice %+v: %v", endpointSlice, err))
		return
	}