Teníamos esta anotación de tipo:

//// tab | Python 3.10+

```Python
q: str | None = None
```

////

//// tab | Python 3.9+

```Python
q: Union[str, None] = None
```

////

Lo que haremos es envolver eso con `Annotated`, para que se convierta en:

//// tab | Python 3.10+

```Python
q: Annotated[str | None] = None
```

////

//// tab | Python 3.9+

```Python

@app.post("/optional-list-str", operation_id="optional_list_str")
async def read_optional_list_str(
    p: Annotated[Optional[list[str]], Body(embed=True)] = None,
):
    return {"p": p}


class BodyModelOptionalListStr(BaseModel):
    p: Optional[list[str]] = None


@app.post("/model-optional-list-str", operation_id="model_optional_list_str")
async def read_model_optional_list_str(p: BodyModelOptionalListStr):

    username: str
    password: str
    email: EmailStr
    full_name: Union[str, None] = None


class UserOut(BaseModel):
    username: str
    email: EmailStr
    full_name: Union[str, None] = None


class UserInDB(BaseModel):
    username: str
    hashed_password: str
    email: EmailStr
    full_name: Union[str, None] = None


def fake_password_hasher(raw_password: str):

        "price": 1.0,
        "owner_ids": None,
    }


def test_validlist():
    response = client.get("/items/validlist")
    response.raise_for_status()
    assert response.json() == [
        {
            "name": "foo",
            "date": datetime(2021, 7, 26).isoformat(),
            "price": None,
            "owner_ids": None,
        },
        {
            "name": "bar",

from typing import Union

from fastapi import APIRouter, FastAPI
from pydantic import BaseModel, HttpUrl

app = FastAPI()


class Invoice(BaseModel):
    id: str
    title: Union[str, None] = None
    customer: str
    total: float


class InvoiceEvent(BaseModel):
    description: str
    paid: bool


class InvoiceEventReceived(BaseModel):
    ok: bool


invoices_callback_router = APIRouter()

    name: Optional[str] = None
    call: Optional[Callable[..., Any]] = None
    request_param_name: Optional[str] = None
    websocket_param_name: Optional[str] = None
    http_connection_param_name: Optional[str] = None
    response_param_name: Optional[str] = None
    background_tasks_param_name: Optional[str] = None
    security_scopes_param_name: Optional[str] = None
    own_oauth_scopes: Optional[list[str]] = None

                                    message);
                        }
                    } else {
                        done = true;
                    }
                } else {
                    done = true;
                }
            }
        } while (!done);

        ProjectRelocation rel = new ProjectRelocation();
        rel.project = project;
        rel.pomArtifact = pomArtifact;

    assert response.json() == {
        "detail": [
            {
                "type": "missing",
                "loc": ["cookie", "p"],
                "msg": "Field required",
                "input": IsOneOf(None, {}),
            }
        ]
    }


@pytest.mark.parametrize(
    "path",
    ["/required-str", "/model-required-str"],
)
def test_required_str(path: str):
    client = TestClient(app)

	ctx, done, err := p.TrackDiskHealth(ctx, storageMetricListVols, "/")
	if err != nil {
		return nil, err
	}
	defer done(0, &err)

	return p.storage.ListVols(ctx)
}

func (p *xlStorageDiskIDCheck) StatVol(ctx context.Context, volume string) (vol VolInfo, err error) {
	ctx, done, err := p.TrackDiskHealth(ctx, storageMetricStatVol, volume)
	if err != nil {
		return vol, err
	}
	defer done(0, &err)

class Token(BaseModel):
    access_token: str
    token_type: str


class TokenData(BaseModel):
    username: Union[str, None] = None


class User(BaseModel):
    username: str
    email: Union[str, None] = None
    full_name: Union[str, None] = None
    disabled: Union[bool, None] = None


class UserInDB(User):
    hashed_password: str


password_hash = PasswordHash.recommended()