///

/// tip

Notice that in this case we are using a standard Python `open()` function that interacts with a file.

So, it involves I/O (input/output), that requires "waiting" for things to be written to disk.

But `open()` doesn't use `async` and `await`.

So, we declare the event handler function with standard `def` instead of `async def`.

///

            str,
            Doc(
                """
                A path prefix handled by a proxy that is not seen by the application
                but is seen by external clients, which affects things like Swagger UI.

                Read more about it at the
                [FastAPI docs for Behind a Proxy](https://fastapi.tiangolo.com/advanced/behind-a-proxy/).

                **Example**

//// tab | Тест

Вот некоторые элементы, обёрнутые в HTML-элементы "abbr" (часть выдумана):

### abbr даёт полную расшифровку { #the-abbr-gives-a-full-phrase }

* <abbr title="Getting Things Done – Как привести дела в порядок">GTD</abbr>
* <abbr title="less than – меньше чем"><code>lt</code></abbr>
* <abbr title="XML Web Token – XML веб‑токен">XWT</abbr>

for this service if you wish); that you receive source code or can get
it if you want it; that you can change the software and use pieces of
it in new free programs; and that you are informed that you can do
these things.

  To protect your rights, we need to make restrictions that forbid
distributors to deny you these rights or to ask you to surrender these
rights.  These restrictions translate to certain responsibilities for

For example, there's an official <a href="https://hub.docker.com/_/python" class="external-link" target="_blank">Python Image</a>.

And there are many other images for different things like databases, for example for:

* <a href="https://hub.docker.com/_/postgres" class="external-link" target="_blank">PostgreSQL</a>
* <a href="https://hub.docker.com/_/mysql" class="external-link" target="_blank">MySQL</a>

This idea of **asynchronous** code described above is also sometimes called **"concurrency"**. It is different from **"parallelism"**.

**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

//// tab | Test

Hier einige Dinge, die in HTML-„abbr“-Elemente gepackt sind (einige sind erfunden):

### Das abbr gibt eine vollständige Phrase { #the-abbr-gives-a-full-phrase }

* <abbr title="Getting Things Done – Dinge erledigt bekommen">GTD</abbr>
* <abbr title="less than – kleiner als"><code>lt</code></abbr>
* <abbr title="XML Web Token">XWT</abbr>
* <abbr title="Paralleles Server-Gateway-Interface">PSGI</abbr>

             * request. However the chances are slim and the
             * retry code should ensure the overall request
             * is serviced. The alternative complicates things
             * more than I think is worth it.
             */

            if (socket != null) {
                socket.close();
                socket = null;
            }
            thread = null;

         * same—hence the try-catch here.
         *
         * (Really, we're fortunate that breaking AtomicReferenceFieldUpdater doesn't break _even
         * more_ things.)
         */
        helper = new SynchronizedHelper();
      }
    }
    ATOMIC_HELPER = helper;

    // Prevent rare disastrous classloading in first call to LockSupport.park.

//// tab | Prueba

Aquí algunas cosas envueltas en elementos HTML "abbr" (algunas son inventadas):

### El abbr da una frase completa { #the-abbr-gives-a-full-phrase }

* <abbr title="Getting Things Done – Hacer las cosas">GTD</abbr>
* <abbr title="less than – menor que"><code>lt</code></abbr>
* <abbr title="XML Web Token – Token web XML">XWT</abbr>