Using `Depends(scope="function")`, the exit code after `yield` is executed right after the *path operation function* is finished, before the response is sent back to the client.

And when using `Depends(scope="request")` (the default), the exit code after `yield` is executed after the response is sent.

它被直接导入/包含到FastAPI以便你可以从 `fastapi` 导入，并避免意外从 `starlette.background` 导入备用的 `BackgroundTask` (后面没有 `s`)。

通过仅使用 `BackgroundTasks` (而不是 `BackgroundTask`)，使得能将它作为 *路径操作函数* 的参数 ，并让**FastAPI**为您处理其余部分, 就像直接使用 `Request` 对象。

在FastAPI中仍然可以单独使用 `BackgroundTask`，但您必须在代码中创建对象，并返回包含它的Starlette `Response`。

type lockRequesterInfo struct {
	Name            string // name of the resource lock was requested for
	Writer          bool   // Bool whether write or read lock.
	UID             string // UID to uniquely identify request of client.
	Timestamp       int64  // Timestamp set at the time of initialization.
	TimeLastRefresh int64  // Timestamp for last lock refresh.

Entonces podemos declarar `tags` como un conjunto de strings:

{* ../../docs_src/body_nested_models/tutorial003_py310.py hl[12] *}

Con esto, incluso si recibes un request con datos duplicados, se convertirá en un conjunto de elementos únicos.

Y siempre que emitas esos datos, incluso si la fuente tenía duplicados, se emitirá como un conjunto de elementos únicos.

	// Number of total items where healing failed against item type
	healFailedItemsMap map[madmin.HealItemType]int64

	// The time of the last scan/heal activity
	lastHealActivity time.Time

	// Holds the request-info for logging
	ctx context.Context

	// used to lock this structure as it is concurrently accessed
	mutex sync.RWMutex
}

// NewHealSequence - creates healSettings, assumes bucket and

		return
	default:
		list.eventsSkipped.Add(1)
		err := fmt.Errorf("concurrent target notifications exceeded %d, configured notification target is too slow to accept events for the incoming request rate", maxConcurrentAsyncSend)
		for id := range targetIDset {
			reqInfo := &logger.ReqInfo{}
			reqInfo.AppendTags("targetID", id.String())

Usando `Depends(scope="function")`, el código de salida después de `yield` se ejecuta justo después de que la *path operation function* termina, antes de que la response se envíe de vuelta al cliente.

Y al usar `Depends(scope="request")` (el valor por defecto), el código de salida después de `yield` se ejecuta después de que la response es enviada.

        return pluginArtifact;
    }

    /**
     * Gets the project building request from which this project instance was created. <strong>Warning:</strong> This is
     * a utility method that is meant to assist integrators of Maven, it must not be used by Maven plugins.
     *
     * @return The project building request or {@code null}.
     * @since 2.1
     */
    @Deprecated

这里使用的也是之前创建的 OAuth2 方案，并把它声明为依赖项：`oauth2_scheme`。

该依赖项函数本身不需要作用域，因此，可以使用 `Depends` 和 `oauth2_scheme`。不需要指定安全作用域时，不必使用 `Security`。

此处还声明了从 `fastapi.security` 导入的 `SecurityScopes` 类型的特殊参数。

`SecuriScopes` 类与 `Request` 类似（`Request` 用于直接提取请求对象）。

{* ../../docs_src/security/tutorial005.py hl[8,105] *}

## 使用 `scopes`

参数 `security_scopes` 的类型是 `SecurityScopes`。

它的属性 `scopes`  是作用域列表，所有依赖项都把它作为子依赖项。也就是说所有**依赖**……这听起来有些绕，后文会有解释。

sequenceDiagram
    participant Client
    participant Proxy as Proxy/Load Balancer
    participant Server as FastAPI Server

    Client->>Proxy: HTTPS Request<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: Proxy adds forwarded headers

    Proxy->>Server: HTTP Request<br/>X-Forwarded-For: [client IP]<br/>X-Forwarded-Proto: https<br/>X-Forwarded-Host: mysuperapp.com<br/>Path: /items