              withTopOffset top: CGFloat = 0,
              bottomOffset bottom: CGFloat = 0,
              layout: LayoutMode = .constraints) -> BorderView {
-        let borderView: BorderView
+        var borderView: BorderView
         
         switch layout {
         case .constraints:

    required public init(coder: NSCoder) {
        fatalError("You shouldn't create a BorderView this way.")
    }
}

fileprivate extension UIView {

     */
    @discardableResult
    func add(top border: BorderViewProperties,
             withLeftOffset left: CGFloat = 0,
             rightOffset right: CGFloat = 0,
             layout: LayoutMode = .constraints) -> BorderView {
        var borderView: BorderView
        
        switch layout {
        case .constraints:
