I've used the tool pyupgrade[^1] to perform this cleanup, using the
following command:

```console
$ find examples fastapi_hypermodel tests -name "*.py" \
    -exec pyupgrade --py37-plus {} \;
```

It could be useful to add this weapon in tox test suite for instance.

[^1]: https://github.com/asottile/pyupgrade

I would remove Pydantic as a dependency for this project as it's already
a dependency of FastAPI[^1] itself.

[^1]: https://github.com/tiangolo/fastapi/blob/master/pyproject.toml#L45

Unless I'm mistaken, these two dependencies are not used in the project.
I would remove them as well.

I didn't find any usage of this method in the project. And since it was
defined with a protected scope (by convention), I don't think it should
be used somewhere else.

Instead of keeping a reference to the FastAPI app, I think it's better
to keep its routes. This way, on `HALFor()`, it's more convenient to
retrieve a given route by its endpoint (aka route.name) rather than
iterate on app.routes at every call.

Co-authored-by: Nicolas Dubois <nicolas.c.dubois@gmail.com>

This reverts commit 08145f9.