func collectionview
func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, heightForHeaderInSection section: Int) -> Float
func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, heightForFooterInSection section: Int) -> Float
func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, insetForSection section: Int) -> UIEdgeInsets
func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, insetForHeaderInSection section: Int) -> UIEdgeInsets
func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, insetForFooterInSection section: Int) -> UIEdgeInsets
func collectionView(_ collectionView: UICollectionView, layout: UICollectionViewLayout, minimumInteritemSpacingForSection section: Int) -> Float