code: func (cs *CSCloud) UpdateLoadBalancer(ctx context.Context, clusterName string, service *v1.Service, nodes []*v1.Node) error {
  	klog.V(4).Infof("UpdateLoadBalancer(%v, %v, %v, %v)", clusterName, service.Namespace, service.Name, nodes)
  
  	// Get the load balancer details and existing rules.
  	lb, err := cs.getLoadBalancer(service)
  	if err != nil {
  		return err
  	}
  
  	// Verify that all the hosts belong to the same network, and retrieve their ID's.
  	lb.hostIDs, _, err = cs.verifyHosts(nodes)
  	if err != nil {
  		return err
  	}
  
  	for _, lbRule := range lb.rules {
  		p := lb.LoadBalancer.NewListLoadBalancerRuleInstancesParams(lbRule.Id)
  
  		// Retrieve all VMs currently associated to this load balancer rule.
  		l, err := lb.LoadBalancer.ListLoadBalancerRuleInstances(p)
  		if err != nil {
  			return fmt.Errorf("error retrieving associated instances: %v", err)
  		}
  
  		assign, remove := symmetricDifference(lb.hostIDs, l.LoadBalancerRuleInstances)
  
  		if len(assign) > 0 {
  			klog.V(4).Infof("Assigning new hosts (%v) to load balancer rule: %v", assign, lbRule.Name)
  			if err := lb.assignHostsToRule(lbRule, assign); err != nil {
  				return err
  			}
  		}
  
  		if len(remove) > 0 {
  			klog.V(4).Infof("Removing old hosts (%v) from load balancer rule: %v", assign, lbRule.Name)
  			if err := lb.removeHostsFromRule(lbRule, remove); err != nil {
  				return err
  			}
  		}
  	}
  
  	return nil
  }
docs: // UpdateLoadBalancer updates hosts under the specified load balancer.