anchor.diff:  /// {@tool dartpad --template=stateful_widget_material}
   /// This example shows a [BottomNavigationBar] as it is used within a [Scaffold]
   /// widget. The [BottomNavigationBar] has three [BottomNavigationBarItem]
  -/// widgets and the [currentIndex] is set to index 0. The selected item is
  +/// widgets, which means it defaults to [BottomNavigationBarType.fixed], and
  +/// the [currentIndex] is set to index 0. The selected item is
   /// amber. The `_onItemTapped` function changes the selected item's index
   /// and displays a corresponding message in the center of the [Scaffold].
  -///
  -/// ![A scaffold with a bottom navigation bar containing three bottom navigation
  -/// bar items. The first one is selected.](https://flutter.github.io/assets-for-api-docs/assets/material/bottom_navigation_bar.png)
   ///
   /// ```dart
   /// int _selectedIndex = 0;
  
positive.code: /// ```
  /// {@end-tool}
  ///
  /// See also:
  ///
  ///  * [BottomNavigationBarItem]
  
negative.code: 
  /// Defines the layout and behavior of a [BottomNavigationBar].
  ///
  /// For a sample on how to use these, please see [BottomNavigationBar].
  /// See also:
  ///
  ///  * [BottomNavigationBar]
  