Python supporte des annotations de type (ou *type hints*) optionnelles.

Ces annotations de type constituent une syntaxe spéciale qui permet de déclarer le <abbr title="par exemple : str, int, float, bool">type</abbr> d'une variable.

En déclarant les types de vos variables, cela permet aux différents outils comme les éditeurs de texte d'offrir un meilleur support.

   * href="https://bugs.openjdk.org/browse/JDK-6409434">JDK-6409434</a> is fixed. It's unclear
   * whether nulls were to be permitted or forbidden, but presumably the eventual fix will be to
   * permit them, as it seems more likely that code would depend on that behavior than on the other.
   * Thus, we say the bug is in set(), which fails to support null.
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection

Tienden a requerir configuraciones más complejas, un gestor de cola de mensajes/trabajos, como RabbitMQ o Redis, pero te permiten ejecutar tareas en segundo plano en múltiples procesos, y especialmente, en múltiples servidores.

 *
 * This implements non-transitional processing by preserving deviation characters.
 *
 * This implementation's STD3 rules are configured to `UseSTD3ASCIIRules=false`. This is
 * permissive and permits the `_` character.
 *
 * [mapping table]: https://www.unicode.org/reports/tr46/#IDNA_Mapping_Table
 * [mapping step]: https://www.unicode.org/reports/tr46/#ProcessingStepMap
 */

 *       with the same key. Some behaviors of {@link Multimap} are left unspecified and are provided
 *       only by the subtypes mentioned below.
 *   <dt>{@link ListMultimap}
 *   <dd>An extension of {@link Multimap} which permits duplicate entries, supports random access of
 *       values for a particular key, and has <i>partially order-dependent equality</i> as defined

   * href="https://bugs.openjdk.org/browse/JDK-6409434">JDK-6409434</a> is fixed. It's unclear
   * whether nulls were to be permitted or forbidden, but presumably the eventual fix will be to
   * permit them, as it seems more likely that code would depend on that behavior than on the other.
   * Thus, we say the bug is in set(), which fails to support null.
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection

## Una aplicación con callbacks { #an-app-with-callbacks }

Veamos todo esto con un ejemplo.

Imagina que desarrollas una aplicación que permite crear facturas.

Estas facturas tendrán un `id`, `title` (opcional), `customer` y `total`.

El usuario de tu API (un desarrollador externo) creará una factura en tu API con un request POST.

Luego tu API (imaginemos):

* La documentación interactiva de la API se actualizará automáticamente, incluyendo el nuevo body:

![Swagger UI](https://fastapi.tiangolo.com/img/index/index-03-swagger-02.png)

* Haz clic en el botón "Try it out", te permite llenar los parámetros e interactuar directamente con la API:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

Elas tendem a exigir configurações mais complexas, um gerenciador de fila de mensagens/tarefas, como RabbitMQ ou Redis, mas permitem executar tarefas em segundo plano em vários processos e, especialmente, em vários servidores.

        "config_cache:not_yet_implemented:secrets",
        "config_cache:not_implemented:store_parallel_execution",
        "config_cache:not_yet_implemented:storing_lambdas",
        // reroute to cookbook, no anchors needed
        "build_jenkins",
        "build_teamcity",
        "build_github_actions",
        "sec:configure_github_actions",
        "build_travis",