@SuppressWarnings("unchecked")
    private static Class<Service<?, ?>> serviceType(Service<?, ?> service) {
        return (Class<Service<?, ?>>) service.getClass();
    }
Tests if a user can write a decorator with working as() and serviceAdded() using lambda expressions only.
core/src/test/java/com/linecorp/armeria/server/ServiceTest.java