FoldingCell has two main parts: a foregroundView and a containerView. The foregroundView is shown when the cell is in its collapsed state, and the containerView is shown when the cell is opened.
To create a FoldingCell, you must initialize the two above views, as well as a top constraint for each of them, named foregroundViewTop and containerViewTop, respectively. In the example, these are created with EasyPeasy, a library which provides convenient syntax for working with constraints programmatically.
Finally, you'll want to override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) in your TableViewController and call cell.selectedAnimation to play the folding animation. You'll also want to animate the table view to account for the new height of the cell.
And that's all!