1. Import

lib/content_views/utils/widget_stack.dart

@@ -0,0 +1,17 @@
+class WidgetStack<E> {
+  final _list = <E>[];
+
+  void push(E value) => _list.add(value);
+
+  E pop() => _list.removeLast();
+
+  E get peek => _list.last;
+
+  bool get isEmpty => _list.isEmpty;
+  bool get isNotEmpty => _list.isNotEmpty;
+
+  void clear() => _list.clear();
+
+  @override
+  String toString() => _list.toString();
+}