These functions can be declared with `async def` or normal `def`.

### `startup` event { #startup-event }

To add a function that should be run before the application starts, declare it with the event `"startup"`:

{* ../../docs_src/events/tutorial001_py310.py hl[8] *}

Si no se especifica y la dependencia tiene `yield`, tendrá un `scope` de `"request"` por defecto.

### `scope` para sub-dependencias { #scope-for-sub-dependencies }

Cuando declaras una dependencia con `scope="request"` (el valor por defecto), cualquier sub-dependencia también necesita tener un `scope` de `"request"`.

  }

  /**
   * Compares two comparable objects as specified by {@link Comparable#compareTo}, <i>if</i> the
   * result of this comparison chain has not already been determined.
   *
   * <p>This method is declared to accept any 2 {@code Comparable} objects, even if they are not <a
   * href="https://docs.oracle.com/javase/tutorial/collections/interfaces/order.html">mutually

    public void testMethodOverrides() throws NoSuchMethodException {
        // Given
        Class<?> clazz = SmbComTreeDisconnect.class;

        // When & Then - verify methods are declared in this class (overridden)
        Method writeParameterWords = clazz.getDeclaredMethod("writeParameterWordsWireFormat", byte[].class, int.class);
        assertNotNull(writeParameterWords);

If you go to `/docs`, you will see that it has the **schemas** for the data to be sent in requests and received in responses:

<img src="/img/tutorial/generate-clients/image01.png">

You can see those schemas because they were declared with the models in the app.

That information is available in the app's **OpenAPI schema**, and then shown in the API docs.

Each "scope" is just a string (without spaces).

They are normally used to declare specific security permissions, for example:

* `users:read` or `users:write` are common examples.
* `instagram_basic` is used by Facebook / Instagram.
* `https://www.googleapis.com/auth/drive` is used by Google.

/// info

In OAuth2 a "scope" is just a string that declares a specific permission required.

</div>

### Crear el objeto `Settings` { #create-the-settings-object }

Importa `BaseSettings` de Pydantic y crea una sub-clase, muy similar a un modelo de Pydantic.

De la misma forma que con los modelos de Pydantic, declaras atributos de clase con anotaciones de tipos, y posiblemente, valores por defecto.

By default FastAPI returns JSON responses.

If you declare a [Response Model](../tutorial/response-model.md) FastAPI will use it to serialize the data to JSON, using Pydantic.

If you don't declare a response model, FastAPI will use the `jsonable_encoder` explained in [JSON Compatible Encoder](../tutorial/encoder.md) and put it in a `JSONResponse`.

<img src="/img/tutorial/generate-clients/image01.png">

Vous voyez ces schémas parce qu’ils ont été déclarés avec les modèles dans l’application.

Ces informations sont disponibles dans le **schéma OpenAPI** de l’application, puis affichées dans la documentation de l’API.

</div>

### Créer l'objet `Settings` { #create-the-settings-object }

Importez `BaseSettings` depuis Pydantic et créez une sous-classe, comme pour un modèle Pydantic.

De la même manière qu'avec les modèles Pydantic, vous déclarez des attributs de classe avec des annotations de type, et éventuellement des valeurs par défaut.