Flask 1.0 Released(palletsprojects.com)

    class Route(typing.NamedTuple):
        path: typing.re.Pattern
        method: str
        handler: http.Handler

    class Router:
        def __init__(self, routes: typing.List[Route]) -> None:
            self.routes = routes

        def serve_http(self, r: http.Request) -> http.Response:
            """serve_http implements the http.Handler interface"""
            for route in self.routes:
                if route.path.matches(r.path):
                    return route.handler(r)
            return http.NotFound("404 NOT FOUND")

    class Server(typing.NamedTuple):
        db: DBConnPool

        def first_route(self, r: http.Request) -> http.Response:
            """first_route uses shared `db` resource."""
            pass

        def second_route(self, r: http.Request) -> http.Response:
            """second_route uses shared `db` resource too!"""
            pass