inheritFromWidgetOfExactType isn't defined.

[pacifire]

static AppState of(BuildContext context) {
    return context.inheritFromWidgetOfExactType(AppState);
  }

The method 'inheritFromWidgetOfExactType' isn't defined for the type 'BuildContext'. Try correcting the name to the name of an existing method, or defining a method named 'inheritFromWidgetOfExactType'.dart(undefined_method)