}

  @GwtIncompatible
  @J2ktIncompatible
  /*
   * The mainline copy of ImmutableMapValues doesn't produce this serialized form anymore, though
   * the backport does. For now, we're keeping the class declaration in *both* flavors so that both
   * flavors can read old data or data from the other flavor. However, we strongly discourage
   * relying on this, as we have made incompatible changes to serialized forms in the past and

To create the callback *path operation* use the same `APIRouter` you created above.

It should look just like a normal FastAPI *path operation*:

* It should probably have a declaration of the body it should receive, e.g. `body: InvoiceEvent`.
* And it could also have a declaration of the response it should return, e.g. `response_model=InvoiceEventReceived`.

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[14:16,19:20,26:30] *}

///

## Duplicate headers { #duplicate-headers }

It is possible to receive duplicate headers. That means, the same header with multiple values.

You can define those cases using a list in the type declaration.

You will receive all the values from the duplicate header as a Python `list`.

For example, to declare a header of `X-Token` that can appear more than once, you can write:

Cela vous donne beaucoup de flexibilité. Vous pouvez retourner n'importe quel type de données, surcharger n'importe quelle déclaration ou validation de données.

## Utiliser le `jsonable_encoder` dans une `Response`

    }
  }

  /**
   * Returns a new {@link TypeVariable} that belongs to {@code declaration} with {@code name} and
   * {@code bounds}.
   */
  static <D extends GenericDeclaration> TypeVariable<D> newArtificialTypeVariable(
      D declaration, String name, Type... bounds) {
    return newTypeVariableImpl(
        declaration, name, (bounds.length == 0) ? new Type[] {Object.class} : bounds);
  }

It won't do any data conversion with Pydantic models, it won't convert the contents to any type, etc.

This gives you a lot of flexibility. You can return any data type, override any data declaration or validation, etc.

## Using the `jsonable_encoder` in a `Response` { #using-the-jsonable-encoder-in-a-response }

    /**
     * Returns an immutable list of project remote repositories (directly specified or inherited).
     * The repositories are ordered by declaration order, with inherited repositories appearing
     * after directly specified ones.
     *
     * @param project the project
     * @return ordered list of remote repositories
     */
    @Nonnull

 * </ul>
 * <p>Build order: A (weight=3), then B and C (weight=2, ordered by project ID), then D (weight=1)
 * <p>If projects have identical weights and IDs, the order is deterministic but may not preserve
 * the original declaration order.
 *
 * @since 4.0.0
 */
public class SmartProjectComparator {

    private final ProjectDependencyGraph dependencyGraph;
    private final Map<MavenProject, Long> projectWeights;

Dazu müssen Sie direkt auf den Request zugreifen.

{* ../../docs_src/using_request_directly/tutorial001_py39.py hl[1,7:8] *}

Durch die Deklaration eines *Pfadoperation-Funktionsparameters*, dessen Typ der `Request` ist, weiß **FastAPI**, dass es den `Request` diesem Parameter übergeben soll.

/// tip | Tipp

Con **FastAPI** declaras parámetros con anotaciones de tipos y obtienes:

* **Soporte del editor**.
* **Chequeo de tipos**.

...y **FastAPI** usa las mismas declaraciones para:

* **Definir requerimientos**: de parámetros de path de la request, parámetros de query, headers, bodies, dependencias, etc.
* **Convertir datos**: de la request al tipo requerido.