code: func getFirstServiceSelector(pod *v1.Pod, sl algorithm.ServiceLister) (firstServiceSelector labels.Selector) {
  	if services, err := sl.GetPodServices(pod); err == nil && len(services) > 0 {
  		return labels.SelectorFromSet(services[0].Spec.Selector)
  	}
  	return nil
  }
docs: // getFirstServiceSelector returns one selector of services the given pod.