CollectionViewModel.swift

private func update() {
    var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
    snapshot.appendSections([.main])
    snapshot.appendItems(items.value)
    dataSource?.apply(snapshot)
}
    
public func add(_ items: [Item]) {
    items.forEach {
        self.items.value.append($0)
    }

    update()
}

public func remove(_ items: [Item]) {
    items.forEach { item in
        self.items.value.removeAll { $0 == item }
    }

    update()
}