return (list instanceof RandomAccess)
        ? new RandomAccessWrappedList(key, list, ancestor)
        : new WrappedList(key, list, ancestor);
  }

  /**
   * Collection decorator that stays in sync with the multimap values for a key. There are two kinds
   * of wrapped collections: full and subcollections. Both have a delegate pointing to the
   * underlying collection class.
   *

 * CharEscaper based on the generated array.
 *
 * @author Sven Mawson
 * @since 15.0
 */
@GwtCompatible
public final class CharEscaperBuilder {
  /**
   * Simple decorator that turns an array of replacement char[]s into a CharEscaper, this results in
   * a very fast escape method.
   */
  private static final class CharArrayDecorator extends CharEscaper {

///

## Create a middleware { #create-a-middleware }

To create a middleware you use the decorator `@app.middleware("http")` on top of a function.

The middleware function receives:

* The `request`.
* A function `call_next` that will receive the `request` as a parameter.

    * Puedes tener objetos JSON profundamente **anidados** y validarlos todos y anotarlos.
* **Extensible**:
    * Pydantic permite definir tipos de datos personalizados o puedes extender la validación con métodos en un modelo decorados con el decorador validator.

```Python
def get_settings():
    return Settings()
```

we would create that object for each request, and we would be reading the `.env` file for each request. ⚠️

But as we are using the `@lru_cache` decorator on top, the `Settings` object will be created only once, the first time it's called. ✔️

{* ../../docs_src/settings/app03_an_py39/main.py hl[1,11] *}

Pero también puedes declarar el `Response` que quieres usar (por ejemplo, cualquier subclase de `Response`), en el *path operation decorator* usando el parámetro `response_class`.

Los contenidos que devuelvas desde tu *path operation function* se colocarán dentro de esa `Response`.

/// tip | Consejo

Puedes sobreescribir una dependencia utilizada en cualquier lugar de tu aplicación **FastAPI**.

La dependencia original podría ser utilizada en una *path operation function*, un *path operation decorator* (cuando no usas el valor de retorno), una llamada a `.include_router()`, etc.

FastAPI todavía podrá sobrescribirla.

///

/// tip

You can set a dependency override for a dependency used anywhere in your **FastAPI** application.

The original dependency could be used in a *path operation function*, a *path operation decorator* (when you don't use the return value), a `.include_router()` call, etc.

FastAPI will still be able to override it.

///

But you can also declare the `Response` that you want to be used (e.g. any `Response` subclass), in the *path operation decorator* using the `response_class` parameter.

The contents that you return from your *path operation function* will be put inside of that `Response`.

///

The only new thing is the `callbacks=invoices_callback_router.routes` as an argument to the *path operation decorator*. We'll see what that is next.

## Documenting the callback { #documenting-the-callback }

The actual callback code will depend heavily on your own API app.

And it will probably vary a lot from one app to the next.