* might be absent" as two distinct types in your program, which can aid clarity.
 *
 * <p>Some uses of this class include
 *
 * <ul>
 *   <li>As a method return type, as an alternative to returning {@code null} to indicate that no
 *       value was available
 *   <li>To distinguish between "unknown" (for example, not present in a map) and "known to have no

   * interned, and so does not prevent these instances from being garbage-collected. This most
   * likely does not perform as well as {@link #newStrongInterner}, but is the best alternative when
   * the memory usage of that implementation is unacceptable.
   */
  @GwtIncompatible // java.lang.ref.WeakReference
  public static <E> Interner<E> newWeakInterner() {
    return newBuilder().weak().build();

In einigen Fällen möchten Sie möglicherweise die von den Klassen `Request` und `APIRoute` verwendete Logik überschreiben.

Das kann insbesondere eine gute Alternative zur Logik in einer Middleware sein.

Wenn Sie beispielsweise den <abbr title="Anfragekörper">Requestbody</abbr> lesen oder manipulieren möchten, bevor er von Ihrer Anwendung verarbeitet wird.

/// danger | Gefahr

* 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 { #alternative-old-query-as-the-default-value }

    checkHelperVersion(getClass().getClassLoader(), "SafeAtomicHelper");
    checkHelperVersion(NO_ATOMIC_FIELD_UPDATER, "SynchronizedAtomicHelper");

    // Then, run the actual tests under each alternative classloader:

    runTestMethod(NO_ATOMIC_FIELD_UPDATER);
    // TODO(lukes): assert that the logs are full of errors
  }

  /**

# Custom Request and APIRoute class { #custom-request-and-apiroute-class }

In some cases, you may want to override the logic used by the `Request` and `APIRoute` classes.

In particular, this may be a good alternative to logic in a middleware.

For example, if you want to read or manipulate the request body before it is processed by your application.

/// danger

This is an "advanced" feature.

Se importa/incluye directamente en FastAPI para que puedas importarla desde `fastapi` y evitar importar accidentalmente la alternativa `BackgroundTask` (sin la `s` al final) de `starlette.background`.

Sie wird direkt in FastAPI importiert/inkludiert, sodass Sie sie von `fastapi` importieren können und vermeiden, versehentlich das alternative `BackgroundTask` (ohne das `s` am Ende) von `starlette.background` zu importieren.

            try {
                ChannelInfo alternativeChannel = manager.getLoadBalancer().selectChannel(op);
                alternativeChannel.addPendingOperation(op);
                // Operation would be resent on alternative channel
                // For now, skip actual send implementation
            } catch (Exception e) {
                log.error("Failed to redistribute operation", e);

* `app`: the object created inside of `main.py` with the line `app = FastAPI()`.

It is equivalent to:

```Python
from main import app
```

///

Each alternative ASGI server program would have a similar command, you can read more in their respective documentation.

/// warning

Uvicorn and other servers support a `--reload` option that is useful during development.