dependOnInheritedElement method Null safety

Implementation

@override
InheritedWidget dependOnInheritedElement(Element ancestor, { Object? aspect }) {
  assert(ancestor != null);
  assert(() {
    final Type targetType = ancestor.widget.runtimeType;
    if (state._debugLifecycleState == _StateLifecycle.created) {
      throw FlutterError.fromParts(<DiagnosticsNode>[
        ErrorSummary('dependOnInheritedWidgetOfExactType<$targetType>() or dependOnInheritedElement() was called before ${state.runtimeType}.initState() completed.'),
        ErrorDescription(
          'When an inherited widget changes, for example if the value of Theme.of() changes, '
          "its dependent widgets are rebuilt. If the dependent widget's reference to "
          'the inherited widget is in a constructor or an initState() method, '
          'then the rebuilt dependent widget will not reflect the changes in the '
          'inherited widget.',
        ),
        ErrorHint(
          'Typically references to inherited widgets should occur in widget build() methods. Alternatively, '
          'initialization based on inherited widgets can be placed in the didChangeDependencies method, which '
          'is called after initState and whenever the dependencies change thereafter.',
        ),
      ]);
    }
    if (state._debugLifecycleState == _StateLifecycle.defunct) {
      throw FlutterError.fromParts(<DiagnosticsNode>[
        ErrorSummary('dependOnInheritedWidgetOfExactType<$targetType>() or dependOnInheritedElement() was called after dispose(): $this'),
        ErrorDescription(
          'This error happens if you call dependOnInheritedWidgetOfExactType() on the '
          'BuildContext for a widget that no longer appears in the widget tree '
          '(e.g., whose parent widget no longer includes the widget in its '
          'build). This error can occur when code calls '
          'dependOnInheritedWidgetOfExactType() from a timer or an animation callback.',
        ),
        ErrorHint(
          'The preferred solution is to cancel the timer or stop listening to the '
          'animation in the dispose() callback. Another solution is to check the '
          '"mounted" property of this object before calling '
          'dependOnInheritedWidgetOfExactType() to ensure the object is still in the '
          'tree.',
        ),
        ErrorHint(
          'This error might indicate a memory leak if '
          'dependOnInheritedWidgetOfExactType() is being called because another object '
          'is retaining a reference to this State object after it has been '
          'removed from the tree. To avoid memory leaks, consider breaking the '
          'reference to this object during dispose().',
        ),
      ]);
    }
    return true;
  }());
  return super.dependOnInheritedElement(ancestor as InheritedElement, aspect: aspect);
}