// volume's AccessModes as a string
func accessModesIndexFunc(obj interface{}) ([]string, error) {
	if pv, ok := obj.(*v1.PersistentVolume); ok {
		modes := v1helper.GetAccessModesAsString(pv.Spec.AccessModes)
		return []string{modes}, nil
	}
	return []string{""}, fmt.Errorf("object is not a persistent volume: %v", obj)
}

// listByAccessModes returns all volumes with the given set of