"""
        if self.cid is not None:
            fetcher = self._create_credentials_fetcher()
            return RefreshableCredentials.create_from_metadata(
                metadata=fetcher(),
                refresh_using=fetcher,
                method=self.METHOD,
            )
        else:
            return None

    def _create_credentials_fetcher(self):
        method = self.METHOD

        "name": "Baz",
        "description": None,
        "price": 50.2,
        "tax": 10.5,
        "tags": [],
    }


@needs_py39
def test_put(client: TestClient):
    response = client.put(
        "/items/bar", json={"name": "Barz", "price": 3, "description": None}
    )
    assert response.json() == {
        "name": "Barz",
        "description": None,
        "price": 3,
        "tax": 10.5,

At a minimum, that file should contain either a full sentence or a TODO,
ideally referring to a person with the responsibility to complete the note.

If your CL addresses an accepted proposal, mention the proposal issue number in
your release note in the form `/issue/NUMBER`. A link to the issue in the text
will have this form (see below). If you don't want to mention the issue in the
text, add it as a comment:
```

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


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


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):

    "ci.pipeline.run.id=${PROW_JOB_ID},"\
    "ci.pipeline.run.repo=${REPO_OWNER:-unknown}/${REPO_NAME:-unknown},"\
    "ci.pipeline.run.base=${PULL_BASE_REF:-none},"\
    "ci.pipeline.run.pull_number=${PULL_NUMBER:-none},"\
    "ci.pipeline.run.pull_sha=${PULL_PULL_SHA:-${PULL_BASE_SHA:-none}}"
}

# Usage: tracing::run <span name> [command ...]
function tracing::run() {

<img src="/img/tutorial/response-status-code/image01.png">

/// note | "Hinweis"

Einige Responsecodes (siehe nächster Abschnitt) kennzeichnen, dass die Response keinen Body hat.

FastAPI versteht das und wird in der OpenAPI-Dokumentation anzeigen, dass es keinen Responsebody gibt.

///

## Über HTTP-Statuscodes

/// note | "Hinweis"

<img src="/img/tutorial/response-status-code/image01.png">

/// note | "Примечание"

Некоторые коды статуса ответа (см. следующий раздел) указывают на то, что ответ не имеет тела.

FastAPI знает об этом и создаст документацию OpenAPI, в которой будет указано, что тело ответа отсутствует.

///

## Об HTTP кодах статуса ответа

/// note | "Примечание"

    client = TestClient(app)
    return client


@needs_py310
@pytest.mark.parametrize(
    "path,headers,expected_status,expected_response",
    [
        ("/items", None, 200, {"X-Token values": None}),
        ("/items", {"x-token": "foo"}, 200, {"X-Token values": ["foo"]}),
        # TODO: fix this, is it a bug?

      }
    }

    /**
     * Returns true if none of the Vary headers have changed between [cachedRequest] and
     * [newRequest].
     */
    fun varyMatches(
      cachedResponse: Response,
      cachedRequest: Headers,
      newRequest: Request,
    ): Boolean {
      return cachedResponse.headers.varyFields().none {
        cachedRequest.values(it) != newRequest.headers(it)
      }
    }

			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
			return
		}
	}

	q := r.Form
	node := q.Get("node")

	keepAliveTicker := time.NewTicker(500 * time.Millisecond)
	defer keepAliveTicker.Stop()

	mrfCh, err := globalNotificationSys.GetReplicationMRF(ctx, bucket, node)
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}