Ele não consegue lidar muito bem com modelos aninhados. Então, se o corpo JSON na requisição for um objeto JSON que contém campos internos que por sua vez são objetos JSON aninhados, ele não consegue ser documentado e validado apropriadamente.

/// tip

Pydantic 是 FastAPI 中所有数据验证和序列化的核心，当你在没有设默认值的情况下使用 `Optional` 或 `Union[Something, None]` 时，它具有特殊行为，你可以在 Pydantic 文档中阅读有关<a href="https://docs.pydantic.dev/latest/concepts/models/#required-optional-fields" class="external-link" target="_blank">必需可选字段</a>的更多信息。

///

## 查询参数列表 / 多个值

当你使用 `Query` 显式地定义查询参数时，你还可以声明它去接收一组值，或换句话来说，接收多个值。

例如，要声明一个可在 URL 中出现多次的查询参数 `q`，你可以这样写：

    full_name = user_dict["full_name"],
    disabled = user_dict["disabled"],
    hashed_password = user_dict["hashed_password"],
)
```

/// info | 说明

`user_dict` 的说明，详见[**更多模型**一章](../extra-models.md#user_indict){.internal-link target=_blank}。

///

## 返回 Token

`token` 端点的响应必须是 JSON 对象。

响应返回的内容应该包含 `token_type`。本例中用的是**Bearer**Token，因此， Token 类型应为**`bearer`**。

    * Convert Python types (`str`, `int`, `float`, `bool`, `list`, etc).
    * `datetime` objects.
    * `UUID` objects.
    * Database models.
    * ...and many more.
* Automatic interactive API documentation, including 2 alternative user interfaces:
    * Swagger UI.
    * ReDoc.

---

Coming back to the previous code example, **FastAPI** will:

     *
     * @return the settings instance
     */
    @Nonnull
    Settings getSettings();

    /**
     * Retrieves toolchain models that have been explicitly configured.
     *
     * @return the toolchain models
     */
    @Nonnull
    Collection<ToolchainModel> getToolchains();

    /**
     * Retrieves the local repository associated with this session.
     *

            field_info=FieldInfo(annotation=model),
            name=model.__name__,
            mode="validation",
        )
        for model in flat_validation_models
    ]
    flat_serialization_model_fields = [
        ModelField(
            field_info=FieldInfo(annotation=model),
            name=model.__name__,
            mode="serialization",
        )
        for model in flat_serialization_models
    ]

inside and make sure it is serializable as JSON, using the same [JSON Compatible Encoder](../tutorial/encoder.md){.internal-link target=_blank} explained in the tutorial. This is what allows you to return **arbitrary objects**, for example database models.

But if you are certain that the content that you are returning is **serializable with JSON**, you can pass it directly to the response class and avoid the extra overhead that FastAPI would have by passing your return content through the...

    * les types Python (`str`, `int`, `float`, `bool`, `list`, etc).
    * les objets `datetime`.
    * les objets `UUID`.
    * les modèles de base de données.
    * ... et beaucoup plus.
* La documentation API interactive automatique, avec 2 interfaces utilisateur au choix :
    * Swagger UI.
    * ReDoc.

---

    * Convertir tipos de Python (`str`, `int`, `float`, `bool`, `list`, etc).
    * Objetos `datetime`.
    * Objetos `UUID`.
    * Modelos de base de datos.
    * ...y muchos más.
* Documentación interactiva automática de la API, incluyendo 2 interfaces de usuario alternativas:
    * Swagger UI.
    * ReDoc.

---

    * Converte tipos Python (`str`, `int`, `float`, `bool`, `list` etc).
    * Objetos `datetime`.
    * Objetos `UUID`.
    * Modelos de Banco de Dados.
    * ...e muito mais.
* Documentação interativa automática da API, incluindo 2 alternativas de interface de usuário:
    * Swagger UI.
    * ReDoc.

---