You can override these exception handlers with your own.

### Override request validation exceptions

When a request contains invalid data, **FastAPI** internally raises a `RequestValidationError`.

And it also includes a default exception handler for it.

Then you can write a template at `templates/item.html` with, for example:

```jinja hl_lines="7"
{!../../../docs_src/templates/templates/item.html!}
```

### Template Context Values

In the HTML that contains:

{% raw %}

```jinja
Item ID: {{ id }}
```

{% endraw %}

...it will show the `id` taken from the "context" `dict` you passed:

```Python
{"id": id}
```

When the **container** is started and running (started from a **container image**) it could create or change files, environment variables, etc. Those changes will exist only in that container, but would not persist in the underlying container image (would not be saved to disk).

Wenn Sie in hier **mehrere Container** hätten, würde Prometheus beim **Lesen der Metriken** standardmäßig jedes Mal diejenigen für **einen einzelnen Container** abrufen (für den Container, der den spezifischen Request verarbeitet hat), anstatt die **akkumulierten Metriken** für alle replizierten Container abzurufen.

* `Form()`
* `File()`

The keys of the `dict` identify each example, and each value is another `dict`.

Each specific example `dict` in the `examples` can contain:

* `summary`: Short description for the example.
* `description`: A long description that can contain Markdown text.
* `value`: This is the actual example shown, e.g. a `dict`.

### Model for Output Response Data

If you interact with the docs and check the response, even though the code didn't add anything in one of the `description` fields, the JSON response contains the default value (`null`):

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image02.png">
</div>

    typer.echo(f"Building docs for: {lang}")
    build_site_dist_path = build_site_path / lang
    if lang == "en":
        dist_path = site_path
        # Don't remove en dist_path as it might already contain other languages.
        # When running build_all(), that function already removes site_path.
        # All this is only relevant locally, on GitHub Actions all this is done through

# Status Codes

You can import the `status` module from `fastapi`:

```python
from fastapi import status
```

`status` is provided directly by Starlette.

It contains a group of named constants (variables) with integer status codes.

For example:

* 200: `status.HTTP_200_OK`
* 403: `status.HTTP_403_FORBIDDEN`
* etc.

**FastAPI** will use that *temporal* response to extract the status code (also cookies and headers), and will put them in the final response that contains the value you returned, filtered by any `response_model`.

    In particular, when running on **Kubernetes** you will probably **not** want to use Gunicorn and instead run **a single Uvicorn process per container**, but I'll tell you about it later in that chapter.

## Gunicorn with Uvicorn Workers