@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">
<summary>Ou utilisez <code>async def</code> ...</summary>

Si votre code utilise `async` / `await`, utilisez `async def` :

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")