data: Union[str, None] = Header(
                default=None,
                example="header1",
            ),
        ):
            return data

    @app.get("/header_examples/")
    def header_examples(
        data: Union[str, None] = Header(
            default=None,
            examples=[
                "header1",
                "header2",
            ],
        ),
    ):

                                "Header One": {
                                    "summary": "Header One Summary",
                                    "description": "Header One Description",
                                    "value": "header1",
                                },
                                "Header Two": {"value": "header2"},
                            },
                        }

* «the exception handler»: «der Exceptionhandler»
* «the form model»: «das Formularmodell»
* «the form body»: «der Formularbody»
* «the header»: «der Header»
* «the headers» (plural): «die Header»
* «in headers» (plural): «in Headern»
* «the forwarded header»: «der Forwarded-Header»
* «the lifespan event»: «das Lifespan-Event»
* «the lock»: «der Lock»
* «the locking»: «das Locking»

    response = client.get(path, headers=[("p", "hello"), ("p", "world")])
    assert response.status_code == 200
    assert response.json() == {"p": ["hello", "world"]}


# =====================================================================================
# Alias


@app.get("/optional-list-alias")
async def read_optional_list_alias(
    p: Annotated[Optional[list[str]], Header(alias="p_alias")] = None,
):

                "msg": "Field required",
                "input": AnyThing,
            }
        ]
    }


@pytest.mark.parametrize(
    "path",
    ["/required-str", "/model-required-str"],
)
def test_required_str(path: str):
    client = TestClient(app)
    response = client.get(path, headers={"p": "hello"})
    assert response.status_code == 200
    assert response.json() == {"p": "hello"}

    client = TestClient(app)
    response = client.get(path, headers={"p": "hello"})
    assert response.status_code == 200
    assert response.json() == {"p": "hello"}


# =====================================================================================
# Alias


@app.get("/optional-alias")
async def read_optional_alias(
    p: Annotated[Optional[str], Header(alias="p_alias")] = None,
):
    return {"p": p}

                "loc": ["header", "p"],
                "msg": "Field required",
                "input": AnyThing,
            }
        ]
    }


@pytest.mark.parametrize(
    "path",
    ["/required-list-str", "/model-required-list-str"],
)
def test_required_list_str(path: str):
    client = TestClient(app)
    response = client.get(path, headers=[("p", "hello"), ("p", "world")])

    response = client.get("/items?token=jessica", headers={"X-Token": "invalid"})
    assert response.status_code == 400
    assert response.json() == {"detail": "X-Token header invalid"}


def test_items_bar_with_invalid_token(client: TestClient):
    response = client.get("/items/bar?token=jessica", headers={"X-Token": "invalid"})
    assert response.status_code == 400

def test_get_invalid_one_header_items(client: TestClient):
    response = client.get("/items/", headers={"X-Token": "invalid"})
    assert response.status_code == 400, response.text
    assert response.json() == {"detail": "X-Token header invalid"}


def test_get_invalid_one_users(client: TestClient):
    response = client.get("/users/", headers={"X-Token": "invalid"})
    assert response.status_code == 400, response.text

    mod = importlib.import_module(f"docs_src.header_param_models.{request.param}")

    client = TestClient(mod.app)
    client.headers.clear()
    return client


def test_header_param_model(client: TestClient):
    response = client.get(
        "/items/",
        headers=[
            ("save-data", "true"),
            ("if-modified-since", "yesterday"),
            ("traceparent", "123"),