code: private Route _build() {
          Preconditions.checkNotNull(controller);
          Preconditions.checkNotNull(httpMethod);
          Preconditions.checkNotNull(uri);
          Preconditions.checkNotNull(httpMethod);
  
          return new Route(httpMethod, uri, controller, controllerMethod);
      }
docs: Internal method building the route.
  
  @return the route.