code: func (az *Cloud) GetZoneByNodeName(ctx context.Context, nodeName types.NodeName) (cloudprovider.Zone, error) {
  	// Returns "" for unmanaged nodes because azure cloud provider couldn't fetch information for them.
  	unmanaged, err := az.IsNodeUnmanaged(string(nodeName))
  	if err != nil {
  		return cloudprovider.Zone{}, err
  	}
  	if unmanaged {
  		klog.V(2).Infof("GetZoneByNodeName: omitting unmanaged node %q", nodeName)
  		return cloudprovider.Zone{}, nil
  	}
  
  	return az.vmSet.GetZoneByNodeName(string(nodeName))
  }
docs: // GetZoneByNodeName implements Zones.GetZoneByNodeName
  // This is particularly useful in external cloud providers where the kubelet
  // does not initialize node data.