{* ../../docs_src/advanced_middleware/tutorial002.py hl[2,6:8] *}

Se soportan los siguientes argumentos:

* `allowed_hosts` - Una list de nombres de dominio que deberían ser permitidos como nombres de host. Se soportan dominios comodín como `*.example.com` para hacer coincidir subdominios. Para permitir cualquier nombre de host, usa `allowed_hosts=["*"]` u omite el middleware.

 * Fix: Use strict timeouts when aborting a download.
 * Fix: Support Shoutcast HTTP responses like `ICY 200 OK`.
 * Fix: Don't unzip if there isn't a response body.
 * Fix: Don't leak gzip streams on redirects.
 * Fix: Don't do DNS lookups on invalid hosts.
 * Fix: Exhaust the underlying stream when reading gzip streams.
 * Fix: Support the `PATCH` method.

     * @param {string} options.cursor – Character to use for cursor, defaults to ▋.
     * @param {Object[]} lineData - Dynamically loaded line data objects.
     * @param {boolean} options.noInit - Don't initialise the animation.
     */
    constructor(container = '#termynal', options = {}) {
        this.container = (typeof container === 'string') ? document.querySelector(container) : container;

    WHITESPACE(CharMatcher.whitespace(), WHITESPACE_CHARACTERS),
    HASH(CharMatcher.is('#'), "#"),
    ASCII(CharMatcher.ascii(), ASCII_CHARACTERS),
    WESTERN_DIGIT("0123456789"),
    ALL_DIGIT(CharMatcher.digit(), ALL_DIGITS),
    OPS_5("+-*/%"),
    HEX_16(CharMatcher.inRange('0', '9').or(CharMatcher.inRange('A', 'F')), "0123456789ABCDEF"),
    HEX_22(
        CharMatcher.inRange('0', '9')

But you don't have to worry about them either, incoming dicts are converted automatically and your output is converted automatically to JSON too.

## Bodies of arbitrary `dict`s { #bodies-of-arbitrary-dicts }

You can also declare a body as a `dict` with keys of some type and values of some other type.

Dans cet exemple, la fonction de tâche écrira dans un fichier (afin de simuler un envoi d'email).

L'opération d'écriture n'utilisant ni `async` ni `await`, on définit la fonction avec un `def` normal.

{* ../../docs_src/background_tasks/tutorial001.py hl[6:9] *}

## Ajouter une tâche d'arrière-plan

    ```

 *  Fix: Don't miss cancels when sending HTTP/2 request headers.
 *  Fix: Don't miss whole operation timeouts when calls redirect.
 *  Fix: Don't leak connections if web sockets have malformed responses or if `onOpen()` throws.
 *  Fix: Don't retry when request bodies fail due to `FileNotFoundException`.
 *  Fix: Don't crash when URLs have IPv4-mapped IPv6 addresses.

          queuedExecutor.execute(queuedTask);
        }
      } finally {
        // Null out the thread field, so that we don't leak a reference to Thread, and so that
        // future `thread == currentThread()` calls from this thread don't incorrectly queue instead
        // of executing. Don't null out the latestTaskQueue field, because the work done here

#### Framed protocols

        .address.url.host
    ) {
      return true // This connection is a perfect match.
    }

    // At this point we don't have a hostname match. But we still be able to carry the request if
    // our connection coalescing requirements are met. See also:
    // https://hpbn.co/optimizing-application-delivery/#eliminate-domain-sharding
    // https://daniel.haxx.se/blog/2016/08/18/http2-connection-coalescing/