e.g., setting the environment variable `TF_ENABLE_MKL_NATIVE_FORMAT` will
    not have any effect.

*   TensorFlow has been validated on Windows Subsystem for Linux 2 (aka WSL 2)
    for both GPUs and CPUs.

*   Due to security issues (see section below), all boosted trees code has been
    deprecated. Users should switch to

app = FastAPI()

@app.get("/items/invalidnone", response_model=Union[Item, None])
def get_invalid_none():
    return None
```

This way the data will be correctly validated, you won't have an internal server error, and the documentation will also reflect that this *path operation* could return `None` (or `null` in JSON).

### Fixes