code: func verify(services corev1.ServiceInterface, stackName string, service string) error {
  	svc, err := services.Get(service, metav1.GetOptions{})
  	if err == nil {
  		if key, ok := svc.ObjectMeta.Labels[labels.ForStackName]; ok {
  			if key != stackName {
  				return fmt.Errorf("service %s already present in stack named %s", service, key)
  			}
  			return nil
  		}
  		return fmt.Errorf("service %s already present in the cluster", service)
  	}
  	return nil
  }
docs: // verify checks whether the service is already present in kubernetes.
  // If we find the service by name but it doesn't have our label or it has a different value
  // than the stack name for the label, we fail (i.e. it will collide)