Optional[int],
            Doc(
                """
                The default status code to be used for the response.

                You could override the status code by returning a response directly.

                Read more about it in the
                [FastAPI docs for Response Status Code](https://fastapi.tiangolo.com/tutorial/response-status-code/).
                """

If you are using `response_model` with some type that doesn't include `None` but the function is returning `None`, it will now raise an internal server error, because you are returning invalid data that violates the contract in `response_model`. Before this release it would allow breaking that contract returning `None`.

For example, if you have an app like this:

```Python
from fastapi import FastAPI