private static Class<?> generatedStub(Annotation annotation, Method valueMethod) {
        try {
            return (Class<?>) valueMethod.invoke(annotation, null);
        } catch (IllegalAccessException | InvocationTargetException e) {
            throw new IllegalArgumentException(
                    "Could not find a gRPC Kotlin generated client stub.", Exceptions.peel(e));
        }
    }
A gRPC client stub factory for <a href="https://github.com/grpc/grpc-kotlin">gRPC-Kotlin</a>.
grpc/src/main/java/com/linecorp/armeria/internal/client/grpc/KotlinGrpcClientStubFactory.java