How to instantiate custom class via GDNative (Question)

What is the correct way to instantiate a custom class and return it to Godot via GDNative?!

(minimal representation below)

```
class A : public Reference {
     Ref<B> create_b()
}

class B : public Reference {
}
```

what should be the body of `create_b()` ?
for future reference the correct way to do this is:

`return Ref<B>::__internal_constructor(B::_new())` ;)