// it refers to a snapshot artifact or meta-version.
        // NOTE: Release metadata includes version information about artifacts that have been released, to allow
        // meta-versions like RELEASE and LATEST to resolve, and also to allow retrieval of the range of valid, released
        // artifacts available.
        ArtifactRepositoryPolicy policy = metadata.getPolicy(repository);

        if (!policy.isEnabled()) {

/// info

FastAPI 通过 Pydantic 模型的 `.dict()` 配合 <a href="https://docs.pydantic.dev/latest/concepts/serialization/#modeldict" class="external-link" target="_blank">该方法的 `exclude_unset` 参数</a> 来实现此功能。

///

/// info

你还可以使用：

* `response_model_exclude_defaults=True`
* `response_model_exclude_none=True`

releases of OkHttp.

ProGuard was the previous default. We’re [tracking problems][proguard_problems] with interactions
between ProGuard, OkHttp 4.x, and Kotlin-originated `.class` files. Make sure you’re on the latest
release if you’re using ProGuard,


Gradle
------

OkHttp 4’s minimum requirements are Java 8+ and Android 5+. These requirements were
[first introduced][require_android_5] with OkHttp 3.13.

{* ../../docs_src/openapi_callbacks/tutorial001_py310.py hl[7:11,34:51] *}

/// tip | Tipp

Der Query-Parameter `callback_url` verwendet einen Pydantic-<a href="https://docs.pydantic.dev/latest/api/networks/" class="external-link" target="_blank">Url</a>-Typ.

///

Das einzig Neue ist `callbacks=invoices_callback_router.routes` als Argument für den *Pfadoperation-Dekorator*. Wir werden als Nächstes sehen, was das ist.

## Technical Details { #technical-details }

Just a technical detail for the curious nerds. 🤓

Underneath, in the ASGI technical specification, this is part of the <a href="https://asgi.readthedocs.io/en/latest/specs/lifespan.html" class="external-link" target="_blank">Lifespan Protocol</a>, and it defines events called `startup` and `shutdown`.

/// info

## Detalhes técnicos { #technical-details }

Apenas um detalhe técnico para nerds curiosos. 🤓

Por baixo, na especificação técnica do ASGI, isso é parte do <a href="https://asgi.readthedocs.io/en/latest/specs/lifespan.html" class="external-link" target="_blank">Protocolo Lifespan</a>, e define eventos chamados `startup` e `shutdown`.

/// info | Informação

## Официальное руководство { #official-guide }

У Pydantic есть официальное <a href="https://docs.pydantic.dev/latest/migration/" class="external-link" target="_blank">руководство по миграции</a> с v1 на v2.

Там также описано, что изменилось, как валидации стали более корректными и строгими, возможные нюансы и т.д.

 *
 * <p>If your iterator supports modification through {@code remove()}, you may wish to override the
 * verify() method, which is called after each sequence and is guaranteed to be called
 * using the latest values obtained from {@link IteratorTester#newTargetIterator()}.
 *
 * <p>The value you pass to the parameter {@code steps} should be greater than the length of your

Además de tipos singulares normales como `str`, `int`, `float`, etc., puedes usar tipos singulares más complejos que heredan de `str`.

Para ver todas las opciones que tienes, revisa el <a href="https://docs.pydantic.dev/latest/concepts/types/" class="external-link" target="_blank">Overview de Tipos de Pydantic</a>. Verás algunos ejemplos en el siguiente capítulo.

为此，请使用 Python 标准类型提示 <a href="https://docs.python.org/3/library/typing.html#typing.Union" class="external-link" target="_blank">`typing.Union`</a>：

/// note | 笔记

定义 <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a> 类型时，要把详细的类型写在前面，然后是不太详细的类型。下例中，更详细的 `PlaneItem` 位于 `Union[PlaneItem，CarItem]` 中的 `CarItem` 之前。

///