code: func SelectableFields(obj *api.Secret) fields.Set {
  	objectMetaFieldsSet := generic.ObjectMetaFieldsSet(&obj.ObjectMeta, true)
  	secretSpecificFieldsSet := fields.Set{
  		"type": string(obj.Type),
  	}
  	return generic.MergeFieldsSets(objectMetaFieldsSet, secretSpecificFieldsSet)
  }
docs: // SelectableFields returns a field set that can be used for filter selection