app = FastAPI()

@app.get("/items/invalidnone", response_model=Item)
def get_invalid_none():
    if flag:
        return {"name": "foo"}
    # if flag is False, at this point the function will implicitly return None
```

If you have *path operations* using `response_model` that need to be allowed to return `None`, make it explicit in `response_model` using `Union[Something, None]`:

    url = ""
    content_type_level = "0"
    if override1:
        url += "/level1"
        content_type_level = "1"
    if override2:
        url += "/level2"
        content_type_level = "2"
    if override3:
        url += "/level3"
        content_type_level = "3"
    if override4:
        url += "/level4"
        content_type_level = "4"
    if override5:
        url += "/override5"