code: func (g *Cloud) GetAllCurrentZones() (sets.String, error) {
  	if g.nodeInformerSynced == nil {
  		klog.Warningf("Cloud object does not have informers set, should only happen in E2E binary.")
  		return g.GetAllZonesFromCloudProvider()
  	}
  	g.nodeZonesLock.Lock()
  	defer g.nodeZonesLock.Unlock()
  	if !g.nodeInformerSynced() {
  		return nil, fmt.Errorf("node informer is not synced when trying to GetAllCurrentZones")
  	}
  	zones := sets.NewString()
  	for zone, nodes := range g.nodeZones {
  		if len(nodes) > 0 {
  			zones.Insert(zone)
  		}
  	}
  	return zones, nil
  }
docs: // GetAllCurrentZones returns all the zones in which k8s nodes are currently running