クロージャの場合は
Cannot convert value of type '(Int, NSCollectionLayoutEnvironment) -> NSCollectionLayoutSection?' (aka '(Int, IBPNSCollectionLayoutEnvironment) -> Optional<IBPNSCollectionLayoutSection>') to expected argument type 'IBPUICollectionViewCompositionalLayoutSectionProvider' (aka '(Int, NSCollectionLayoutEnvironment) -> Optional<NSCollectionLayoutSection>')