```Python hl_lines="35"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

!!! tip
    Notice that you are not passing the router itself (`invoices_callback_router`) to `callback=`, but the attribute `.routes`, as in `invoices_callback_router.routes`.

### Check the docs

---

"*Nós adotamos a biblioteca **FastAPI** para criar um servidor **REST** que possa ser chamado para obter **predições**. [para o Ludwig]*"

That means that, for example, to apply authentication to all the *path operations* in a router it would end up being done in a different file, instead of keeping related logic together.