code: func getDefaultClass(lister storagev1listers.StorageClassLister) (*storagev1.StorageClass, error) {
  	list, err := lister.List(labels.Everything())
  	if err != nil {
  		return nil, err
  	}
  
  	defaultClasses := []*storagev1.StorageClass{}
  	for _, class := range list {
  		if storageutil.IsDefaultAnnotation(class.ObjectMeta) {
  			defaultClasses = append(defaultClasses, class)
  			klog.V(4).Infof("getDefaultClass added: %s", class.Name)
  		}
  	}
  
  	if len(defaultClasses) == 0 {
  		return nil, nil
  	}
  	if len(defaultClasses) > 1 {
  		klog.V(4).Infof("getDefaultClass %d defaults found", len(defaultClasses))
  		return nil, errors.NewInternalError(fmt.Errorf("%d default StorageClasses were found", len(defaultClasses)))
  	}
  	return defaultClasses[0], nil
  }
docs: // getDefaultClass returns the default StorageClass from the store, or nil.