code: func (gce *Cloud) UpdateLoadBalancer(clusterName string, service *v1.Service, nodes []*v1.Node) error {
  	hosts, err := gce.getInstancesByNames(nodeNames(nodes))
  	if err != nil {
  		return err
  	}
  
  	loadBalancerName := cloudprovider.GetLoadBalancerName(service)
  	pool, err := gce.service.TargetPools.Get(gce.projectID, gce.region, loadBalancerName).Do()
  	if err != nil {
  		return err
  	}
  	existing := sets.NewString()
  	for _, instance := range pool.Instances {
  		existing.Insert(hostURLToComparablePath(instance))
  	}
  
  	return gce.updateTargetPool(loadBalancerName, existing, hosts)
  }
docs: // UpdateLoadBalancer is an implementation of LoadBalancer.UpdateLoadBalancer.