Tínhamos esta anotação de tipo:

//// tab | Python 3.10+

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

////

//// tab | Python 3.9+

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

////

O que faremos é envolver isso com `Annotated`, para que fique assim:

//// tab | Python 3.10+

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

////

//// tab | Python 3.9+

```Python

        dependencies: Optional[Sequence[Depends]] = None,
        summary: Optional[str] = None,
        description: Optional[str] = None,
        response_description: str = "Successful Response",
        responses: Optional[dict[Union[int, str], dict[str, Any]]] = None,
        deprecated: Optional[bool] = None,
        methods: Optional[list[str]] = None,
        operation_id: Optional[str] = None,

 *
 */
@Deprecated
public final class ArtifactStatus implements Comparable<ArtifactStatus> {
    /**
     * No trust - no information about status.
     */
    public static final ArtifactStatus NONE = new ArtifactStatus("none", 0);

    /**
     * No trust - information was generated with defaults.
     */
    public static final ArtifactStatus GENERATED = new ArtifactStatus("generated", 1);

    /**

            "price": 50.5,
            "description": None,
            "tax": None,
        },
        "user": {"username": "Dave", "full_name": None},
    }


def test_put_missing_body(client: TestClient):
    response = client.put("/items/5")
    assert response.status_code == 422
    assert response.json() == {
        "detail": [
            {
                "input": None,
                "loc": [

## 선택적 매개변수

같은 방법으로 기본값을 `None`으로 설정하여 선택적 매개변수를 선언할 수 있습니다:

{* ../../docs_src/query_params/tutorial002.py hl[9] *}

이 경우 함수 매개변수 `q`는 선택적이며 기본값으로 `None` 값이 됩니다.

/// check | 확인

**FastAPI**는 `item_id`가 경로 매개변수이고 `q`는 경로 매개변수가 아닌 쿼리 매개변수라는 것을 알 정도로 충분히 똑똑합니다.

///

/// note | 참고

FastAPI는 `q`가 `= None`이므로 선택적이라는 것을 인지합니다.

class Item(BaseModel):
    name: Union[str, None] = None
    description: Union[str, None] = None
    price: Union[float, None] = None
    tax: float = 10.5
    tags: list[str] = []


items = {
    "foo": {"name": "Foo", "price": 50.2},
    "bar": {"name": "Bar", "description": "The bartenders", "price": 62, "tax": 20.2},
    "baz": {"name": "Baz", "description": None, "price": 50.2, "tax": 10.5, "tags": []},
}

        raise ValueError('Invalid ID format, it must start with "isbn-" or "imdb-"')
    return id


@app.get("/items/")
async def read_items(
    id: Annotated[Union[str, None], AfterValidator(check_valid_id)] = None,
):
    if id:
        item = data.get(id)
    else:
        id, item = random.choice(list(data.items()))

        "detail": [
            {
                "type": "missing",
                "loc": ["header", "p_alias"],
                "msg": "Field required",
                "input": IsOneOf(None, IsPartialDict({"p": ["hello", "world"]})),
            }
        ]
    }


@pytest.mark.parametrize(
    "path",
    [
        "/required-list-alias",
        "/model-required-list-alias",

    username: str


def get_current_user(oauth_header: Optional[str] = Security(oid)):
    if oauth_header is None:
        return None
    user = User(username=oauth_header)
    return user


@app.get("/users/me")
def read_current_user(current_user: Optional[User] = Depends(get_current_user)):
    if current_user is None:
        return {"msg": "Create an account first"}
    return current_user


client = TestClient(app)

		for i := range erasureDisks[:8] {
			erasureDisks[i] = nil
		}
		return erasureDisks
	}
	z.serverPools[0].erasureDisksMu.Unlock()

	t.Run("if-none-match with read quorum failure", func(t *testing.T) {
		// Test Case 1: if-none-match (create only if doesn't exist)
		// With if-none-match: *, this should only succeed if object doesn't exist.
		// Since read quorum fails, we can't determine if object exists.
		opts := ObjectOptions{