error Cannot inherit from non-open class 'ListSingleSectionController' outside of its defining module Code (I am new to IOS app development) import Foundation import IGListKit import UIKit import MobileBuySDK class CartBottomSectionController: ListSingleSectionController, CompositionLayoutCapable { func collectionViewSectionLayout(layoutEnvironment: NSCollectionLayoutEnvironment) -> NSCollectionLayoutSection? { let estimation = NSCollectionLayoutDimension.estimated(200) let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: estimation) let item = NSCollectionLayoutItem(layoutSize: itemSize) let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: estimation) let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item]) let section = NSCollectionLayoutSection(group: group) return section } }