{* ../../docs_src/background_tasks/tutorial002_an_py310.py hl[13,15,22,25] *}

Neste exemplo, as mensagens serão escritas no arquivo `log.txt` *após* o envio da resposta.

Se houver uma query na request, ela será registrada em uma tarefa em segundo plano.

E então outra tarefa em segundo plano gerada na *função de operação de rota* escreverá uma mensagem usando o parâmetro de path `email`.

  import tensorflow_io_gcs_filesystem as _tensorflow_io_gcs_filesystem

# Lazy-load Keras v2/3.
_tf_uses_legacy_keras = (
    _os.environ.get("TF_USE_LEGACY_KERAS", None) in ("true", "True", "1"))
setattr(_current_module, "keras", _KerasLazyLoader(globals()))
_module_dir = _module_util.get_parent_dir_for_name("keras._tf_keras.keras")
_current_module.__path__ = [_module_dir] + _current_module.__path__
if _tf_uses_legacy_keras:

Nota que las *path operations* definen los modelos que usan para el payload del request y el payload del response, usando los modelos `Item` y `ResponseMessage`.

### Documentación de la API { #api-docs }

Si vas a `/docs`, verás que tiene los **esquemas** para los datos a enviar en requests y recibir en responses:

<img src="/img/tutorial/generate-clients/image01.png">

Puedes ver esos esquemas porque fueron declarados con los modelos en la app.

En ambos casos, los datos serán convertidos, validados, documentados en el esquema de OpenAPI, etc.

## Úsalo { #use-it }

Ahora puedes declarar tu dependencia usando esta clase.

{* ../../docs_src/dependencies/tutorial002_an_py310.py hl[19] *}

**FastAPI** llama a la clase `CommonQueryParams`. Esto crea una "instance" de esa clase y la instance será pasada como el parámetro `commons` a tu función.

  import tensorflow_io_gcs_filesystem as _tensorflow_io_gcs_filesystem

# Lazy-load Keras v1.
_tf_uses_legacy_keras = (
    _os.environ.get("TF_USE_LEGACY_KERAS", None) in ("true", "True", "1"))
setattr(_current_module, "keras", _KerasLazyLoader(globals(), mode="v1"))
_module_dir = _module_util.get_parent_dir_for_name("keras._tf_keras.keras")
_current_module.__path__ = [_module_dir] + _current_module.__path__
if _tf_uses_legacy_keras:

## Revisa { #check-it }

Ahora, cada request bajo el path `/v1/` será manejado por la aplicación Flask.

Y el resto será manejado por **FastAPI**.

Si lo ejecutas y vas a <a href="http://localhost:8000/v1/" class="external-link" target="_blank">http://localhost:8000/v1/</a> verás el response de Flask:

```txt
Hello, World from Flask!
```

wrapt == 1.16.0
tblib == 2.0.0
ml_dtypes >= 0.5.1, < 0.6.0
auditwheel >= 6.1.0
# Install tensorboard, and keras
# Note that here we want the latest version that matches TF major.minor version
# Note that we must use nightly here as these are used in nightly jobs
# For release jobs, we will pin these on the release branch
keras-nightly ~= 3.10.0.dev
tb-nightly ~= 2.20.0.a

*   Keras 3.0 will be the default Keras version. You may need to update your
    script to use Keras 3.0.

*   Please refer to the new Keras documentation for Keras 3.0
    (https://keras.io/keras_3).

*   To continue using Keras 2.0, do the following.

*   1.  Install tf-keras via pip install tf-keras~=2.16

    1.  To switch tf.keras to use Keras 2 (tf-keras), set the environment

    # via
    #   -r ci/official/requirements_updater/requirements.in
    #   jax
    #   keras-nightly
namex==0.0.8 \
    --hash=sha256:32a50f6c565c0bb10aa76298c959507abdc0e850efe085dc38f3440fcb3aa90b \
    --hash=sha256:7ddb6c2bb0e753a311b7590f84f6da659dd0c05e65cb89d519d54c0a250c0487
    # via keras-nightly
numpy==1.26.4 \
    --hash=sha256:03a8c78d01d9781b28a6989f6fa1bb2c4f2d51201cf99d3dd875df6fbd96b23b \

    # via
    #   -r ci/official/requirements_updater/requirements.in
    #   jax
    #   keras-nightly
namex==0.0.9 \
    --hash=sha256:7bd4e4a2cc3876592111609fdf4cbe6ff19883adbe6b3b40d842fd340f77025e \
    --hash=sha256:8adfea9da5cea5be8f4e632349b4669e30172c7859e1fd97459fdf3b17469253
    # via keras-nightly
numpy==2.1.3 \
    --hash=sha256:016d0f6f5e77b0f0d45d77387ffa4bb89816b57c835580c3ce8e099ef830befe \