### Other utility functions

Any other utility function that you call directly can be created with normal `def` or `async def` and FastAPI won't affect the way you call it.

### Otras funciones de utilidades

Cualquier otra función de utilidad que llames directamente se puede crear con `def` o `async def` normales y FastAPI no afectará la manera en que la llames.

### Diğer yardımcı fonksiyonlar

Doğrudan çağırdığınız diğer herhangi bir yardımcı fonksiyonu, normal "def" veya "async def" ile tanimlayabilirsiniz. FastAPI onu çağırma şeklinizi etkilemez.

But if you go with your browser to <a href="http://127.0.0.1:8000" class="external-link" target="_blank">http://127.0.0.1:8000/app</a> you will see the normal response:

```JSON
{
    "message": "Hello World",
    "root_path": "/api/v1"
}
```

So, it won't expect to be accessed at `http://127.0.0.1:8000/api/v1/app`.

            "",
            display = ParameterDisplay.NORMAL,
            allowEmpty = true,
            description = "The extra gradle parameters you want to pass to this build, e.g. `-PrerunAllTests` or `--no-build-cache`"
        )
        text(
            "reverse.dep.*.additional.gradle.parameters",
            "",
            display = ParameterDisplay.NORMAL,
            allowEmpty = true,

!!! tip
    Also notice that there are `response_models` that have standard Python types like `List[schemas.Item]`.

    But as the content/parameter of that `List` is a Pydantic *model* with `orm_mode`, the data will be retrieved and returned to the client as normally, without problems.

### About `def` vs `async def`

# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

                    .url(normalize(scm.getUrl()))
                    .connection(normalize(scm.getConnection()))
                    .developerConnection(normalize(scm.getDeveloperConnection()))
                    .build());
        }

        DistributionManagement dist = model.getDistributionManagement();
        if (dist != null) {
            Site site = dist.getSite();
            if (site != null) {

    **FastAPI** nie narzuca żadnego konkretnego znaczenia.

    Informacje tutaj są przedstawione jako wskazówka, a nie wymóg.

    Na przykład, używając GraphQL, normalnie wykonujesz wszystkie akcje używając tylko operacji `POST`.

### Krok 4: zdefiniuj **funkcję obsługującą ścieżkę**

To jest nasza "**funkcja obsługująca ścieżkę**":

* **ścieżka**: to `/`.

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you: