!!! tip
    As FastAPI is an async framework, one request could start being processed, and before finishing, another request could be received and start processing as well, and it all could be processed in the same thread.

    /** The key of the message: Could not open {0}. <br/>Please check if the file is associated with an application. */
    public static final String ERRORS_could_not_open_on_system = "{errors.could_not_open_on_system}";

    /** The key of the message: No more results could be displayed. */
    public static final String ERRORS_result_size_exceeded = "{errors.result_size_exceeded}";

This was designed this way mainly to allow using the same objects "yielded" by dependencies inside of background tasks, because the exit code would be executed after the background tasks were finished.

│   └── main.py
```

In the file `main.py` you have your **FastAPI** app:


```Python
{!../../../docs_src/app_testing/main.py!}
```

### Testing file

Then you could have a file `test_main.py` with your tests. It could live on the same Python package (the same directory with a `__init__.py` file):

``` hl_lines="5"
.
├── app
│   ├── __init__.py
│   ├── main.py
│   └── test_main.py
```

## Deployment Strategies

There are several ways to do it depending on your specific use case and the tools that you use.

You could **deploy a server** yourself using a combination of tools, you could use a **cloud service** that does part of the work for you, or other possible options.

     * implement Function<A, B>, as discussed in a class-level comment), it would make some sense to
     * perform runtime null checks on the input and output. (That would also make NullPointerTester
     * happy!) However, since we didn't do that for many years, we're not about to start now.
     * (Runtime checks could be particularly bad for users of LegacyConverter.)
     *

            Any,
            Doc(
                """
                The type to use for the response.

                It could be any valid Pydantic *field* type. So, it doesn't have to
                be a Pydantic model, it could be other things, like a `list`, `dict`,
                etc.

                It will be used for:

	var obj runtime.Object
	var ar *kube.AdmissionReview
	out, _, err := deserializer.Decode(body, nil, obj)
	if err != nil {
		return nil, fmt.Errorf("could not decode body: %v", err)
	}
	ar, err = kube.AdmissionReviewKubeToAdapter(out)
	if err != nil {
		return nil, fmt.Errorf("could not decode object: %v", err)
	}

	return ar.Response.Patch, nil
}

var (
	runtimeScheme = func() *runtime.Scheme {

This way, you could also have an attribute `orion_cat.owner` and the owner would contain the data for this pet's owner, taken from the table *owners*.

So, `orion_cat.owner.name` could be the name (from the `name` column in the `owners` table) of this pet's owner.

It could have a value like `"Arquilian"`.

And the ORM will do all the work to get the information from the corresponding table *owners* when you try to access it from your pet object.

# OpenAPI Webhooks

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps