code: func DropDisabledFields(class, oldClass *storage.StorageClass) {
  	if !utilfeature.DefaultFeatureGate.Enabled(features.ExpandPersistentVolumes) && !allowVolumeExpansionInUse(oldClass) {
  		class.AllowVolumeExpansion = nil
  	}
  }
docs: // DropDisabledFields removes disabled fields from the StorageClass object.