),
        ] = None,
        discriminator: Union[str, None] = None,
        strict: Union[bool, None] = _Unset,
        multiple_of: Union[float, None] = _Unset,
        allow_inf_nan: Union[bool, None] = _Unset,
        max_digits: Union[int, None] = _Unset,
        decimal_places: Union[int, None] = _Unset,
        examples: Optional[List[Any]] = None,
        example: Annotated[

    enemies = Sets.newHashSet("Dick", "Harry", "Tom");
  }

  public void testUnion() {
    Set<String> all = Sets.union(friends, enemies);
    assertEquals(5, all.size());

    ImmutableSet<String> immut = Sets.union(friends, enemies).immutableCopy();
    HashSet<String> mut = Sets.union(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Buck");
    assertEquals(6, all.size());

    headers: Optional[Dict[str, Union[Header, Reference]]] = None
    securitySchemes: Optional[Dict[str, Union[SecurityScheme, Reference]]] = None
    links: Optional[Dict[str, Union[Link, Reference]]] = None
    # Using Any for Specification Extensions
    callbacks: Optional[Dict[str, Union[Dict[str, PathItem], Reference, Any]]] = None
    pathItems: Optional[Dict[str, Union[PathItem, Reference]]] = None

```

Le paramètre de requête `q` a pour type `Union[str, None]` (ou `str | None` en Python 3.10), signifiant qu'il est de type `str` mais pourrait aussi être égal à `None`, et bien sûr, la valeur par défaut est `None`, donc **FastAPI** saura qu'il n'est pas requis.

!!! note
    **FastAPI** saura que la valeur de `q` n'est pas requise grâce à la valeur par défaut `= None`.

def get_graphql_response(
    *,
    settings: Settings,
    query: str,
    after: Union[str, None] = None,
    category_id: Union[str, None] = None,
    discussion_number: Union[int, None] = None,
    discussion_id: Union[str, None] = None,
    comment_id: Union[str, None] = None,
    body: Union[str, None] = None,
) -> Dict[str, Any]:
    headers = {"Authorization": f"token {settings.input_token.get_secret_value()}"}

    enemies = Sets.newHashSet("Dick", "Harry", "Tom");
  }

  public void testUnion() {
    Set<String> all = Sets.union(friends, enemies);
    assertEquals(5, all.size());

    ImmutableSet<String> immut = Sets.union(friends, enemies).immutableCopy();
    HashSet<String> mut = Sets.union(friends, enemies).copyInto(new HashSet<String>());

    enemies.add("Buck");
    assertEquals(6, all.size());

@app.get(
    "/response_model_union-no_annotation-return_model1",
    response_model=Union[User, Item],
)
def response_model_union_no_annotation_return_model1():
    return DBUser(name="John", surname="Doe", password_hash="secret")


@app.get(
    "/response_model_union-no_annotation-return_model2",
    response_model=Union[User, Item],
)
def response_model_union_no_annotation_return_model2():

        function: Callable[..., Any],
        *,
        ref: Union[str, None] = None,
        metadata: Any = None,
        serialization: Any = None,
    ) -> Any:
        return {}

    def get_model_definitions(
        *,
        flat_models: Set[Union[Type[BaseModel], Type[Enum]]],
        model_name_map: Dict[Union[Type[BaseModel], Type[Enum]], str],
    ) -> Dict[str, Any]:

#### <abbr title="Union – Verbund, Einheit‚ Vereinigung: Eines von Mehreren">Union</abbr>

Sie können deklarieren, dass eine Variable einer von **verschiedenen Typen** sein kann, zum Beispiel ein `int` oder ein `str`.

In Python 3.6 und höher (inklusive Python 3.10) können Sie den `Union`-Typ von `typing` verwenden und die möglichen Typen innerhalb der eckigen Klammern auflisten.

class Labels(BaseModel):
    nodes: List[LabelNode]


class ReviewNode(BaseModel):
    author: Union[Author, None] = None
    state: str


class Reviews(BaseModel):
    nodes: List[ReviewNode]


class PullRequestNode(BaseModel):
    number: int
    labels: Labels
    author: Union[Author, None] = None
    title: str
    createdAt: datetime
    state: str
    comments: Comments