https://note.com/kitoko552/n/n101bcc94e5b9

note_n101bcc94e5b9_1.dart

static NavigatorState of(
 BuildContext context, {
 bool rootNavigator = false,
 bool nullOk = false,
}) {
 final NavigatorState navigator = rootNavigator
     ? context.rootAncestorStateOfType(const TypeMatcher<NavigatorState>())
     : context.ancestorStateOfType(const TypeMatcher<NavigatorState>());
 assert(() {
   if (navigator == null && !nullOk) {
     throw FlutterError(
       'Navigator operation requested with a context that does not include a Navigator.\n'
       'The context used to push or pop routes from the Navigator must be that of a '
       'widget that is a descendant of a Navigator widget.'
     );
   }
   return true;
 }());
 return navigator;
}