anchor.diff:  
     ImportController _importController;
   
  -  StreamSubscription<String> _pageIdSubscription;
  +  StreamSubscription<String> _showPageSubscription;
   
     @override
     void initState() {
  
positive.code:     _tabController?.dispose();
      _currentScreen?.dispose();
      appBarAnimation?.dispose();
      _pageIdSubscription?.cancel();
  
      super.dispose();
    }
  
negative.code: 
      _setupTabController();
  
      _showPageSubscription =
          frameworkController.onShowPageId.listen(_showPageById);
    }
  
    @override
  