anchor.diff:  ///
   /// ```dart
   /// // Register the RouteObserver as a navigation observer.
  -/// final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();
  +/// final RouteObserver<ModalRoute> routeObserver = RouteObserver<ModalRoute>();
   /// void main() {
   ///   runApp(MaterialApp(
   ///     home: Container(),
  
positive.code: /// be given with their type arguments. Since the [Route] class and its
  /// subclasses have a type argument, this includes the arguments passed to this
  /// class. Consider using `dynamic` to specify the entire class of routes rather
  /// than only specific subtypes. For example, to watch for all [PageRoute]
  /// variants, the `RouteObserver<PageRoute<dynamic>>` type may be used.
  ///
  /// {@tool snippet}
  ///
  
negative.code: ///   @override
  ///   void didChangeDependencies() {
  ///     super.didChangeDependencies();
  ///     routeObserver.subscribe(this, ModalRoute.of(context)!);
  ///   }
  ///
  ///   @override
  