本吧须知10-24〖吧务公布〗UICollectionViewLayoutAttributes

UICollectionViewLayoutAttributes自定义怎么写？？？
+ (instancetype)layoutAttributesForCellWithIndexPath:(NSIndexPath *)indexPath{
}
+ (instancetype)layoutAttributesForSupplementaryViewOfKind:(NSString *)elementKind withIndexPath:(NSIndexPath *)indexPath{
}
+ (instancetype)layoutAttributesForDecorationViewOfKind:(NSString *)decorationViewKind withIndexPath:(NSIndexPath *)indexPath{
}
怎么重写？？？