* Da Sie diesen in der Funktion als vom Typ `Item` deklariert haben, erhalten Sie die ganze Editor-Unterstützung (Autovervollständigung, usw.) für alle Attribute und deren Typen.
* Eine <a href="https://json-schema.org" class="external-link" target="_blank">JSON Schema</a> Definition für Ihr Modell generieren, welche Sie überall sonst verwenden können, wenn es für Ihr Projekt Sinn macht.

* 以 JSON 形式读取请求体
* （在必要时）把请求体转换为对应的类型
* 校验数据：
    * 数据无效时返回错误信息，并指出错误数据的确切位置和内容
* 把接收的数据赋值给参数 `item`
    * 把函数中请求体参数的类型声明为 `Item`，还能获得代码补全等编辑器支持
* 为模型生成 <a href="https://json-schema.org" class="external-link" target="_blank">JSON Schema</a>，在项目中所需的位置使用
* 这些概图是 OpenAPI 概图的部件，用于 API 文档 <abbr title="用户界面">UI</abbr>

## API 文档

Pydantic 模型的 JSON 概图是 OpenAPI 生成的概图部件，可在 API 文档中显示：

///

It will:

* Return that status code in the response.
* Document it as such in the OpenAPI schema (and so, in the user interfaces):

<img src="/img/tutorial/response-status-code/image01.png">

/// note

Some response codes (see the next section) indicate that the response does not have a body.

  // `distinguisherMethod` defines how to compute the flow distinguisher for requests that match this schema.
  // `nil` specifies that the distinguisher is disabled and thus will always be the empty string.
  // +optional
  optional FlowDistinguisherMethod distinguisherMethod = 3;

  // `rules` describes which requests will match this flow schema. This FlowSchema matches a request if and only if
  // at least one member of rules matches the request.

  // `distinguisherMethod` defines how to compute the flow distinguisher for requests that match this schema.
  // `nil` specifies that the distinguisher is disabled and thus will always be the empty string.
  // +optional
  optional FlowDistinguisherMethod distinguisherMethod = 3;

  // `rules` describes which requests will match this flow schema. This FlowSchema matches a request if and only if
  // at least one member of rules matches the request.

    * **Стандартизированный**: Основан на открытых стандартах API (<a href="https://github.com/OAI/OpenAPI-Specification" class="external-link" target="_blank">OpenAPI</a> и <a href="https://json-schema.org/" class="external-link" target="_blank">JSON Schema</a>) и полностью совместим с ними.

        * Nas respostas, o `set` será convertido para uma `list`.
        * O esquema gerado vai especificar que os valores do `set` são unicos (usando o `uniqueItems` do JSON Schema).
* `bytes`:
    * O `bytes` padrão do Python.
    * Em requisições e respostas será representado como uma `str`.
    * O esquema gerado vai especificar que é uma `str` com o "formato" `binary`.
* `Decimal`:

import "k8s.io/api/core/v1/generated.proto";
import "k8s.io/apimachinery/pkg/apis/meta/v1/generated.proto";
import "k8s.io/apimachinery/pkg/runtime/generated.proto";
import "k8s.io/apimachinery/pkg/runtime/schema/generated.proto";

// Package-wide variables from generator "generated".
option go_package = "k8s.io/api/scheduling/v1beta1";

func (f Factory) UnstructuredClientForMapping(mapping *meta.RESTMapping) (resource.RESTClient, error) {
	return f.full.UnstructuredClientForMapping(mapping)
}

func (f Factory) Validator(validationDirective string) (validation.Schema, error) {
	return f.full.Validator(validationDirective)
}

func (f Factory) OpenAPISchema() (openapi.Resources, error) {
	return f.full.OpenAPISchema()
}

///

FastAPI will now:

* **Validate** the data making sure that the max length is 50 characters
* Show a **clear error** for the client when the data is not valid
* **Document** the parameter in the OpenAPI schema *path operation* (so it will show up in the **automatic docs UI**)

## Alternative (old): `Query` as the default value