register dispatchable wsgi application

def register_app(self, name: str, app: Callable = None) -> Callable:
        """ register dispatchable wsgi application"""
        if app is None:
            def dec(app):
                """ inner decorator for register app """
                assert app is not None
                self.register_app(name, app)
                return app
            return dec
        self.applications[name] = app
        return None