* Datenvalidierung
* Automatische Dokumentation

## Defaultwerte

Da Query-Parameter nicht ein festgelegter Teil des Pfades sind, können sie optional sein und Defaultwerte haben.

Im obigen Beispiel haben sie die Defaultwerte `skip=0` und `limit=10`.

Wenn Sie also zur URL:

```
http://127.0.0.1:8000/items/
```

    </dependency>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t06-d</artifactId>
      <version>1.1</version>
      <type>jar</type>
      <scope>compile</scope>
      <optional>false</optional>
    </dependency>
  </dependencies>

        return AbstractValueGraph.this.outDegree(node);
      }
    };
  }

  @Override
  public Optional<V> edgeValue(N nodeU, N nodeV) {
    return Optional.ofNullable(edgeValueOrDefault(nodeU, nodeV, null));
  }

  @Override
  public Optional<V> edgeValue(EndpointPair<N> endpoints) {
    return Optional.ofNullable(edgeValueOrDefault(endpoints, null));
  }

  @Override

    </dependency>
    <dependency>
      <groupId>maven-test</groupId>
      <artifactId>t08-d</artifactId>
      <version>1.1</version>
      <type>jar</type>
      <scope>compile</scope>
      <optional>false</optional>
    </dependency>
  </dependencies>

    }

    public static Optional<AccessorKey> maybeGetKeyOfOldAccessorOfUpgradedProperty(JApiCompatibility jApiCompatibility, ViolationCheckContext context) {
        if (!(jApiCompatibility instanceof JApiMethod) || !((JApiMethod) jApiCompatibility).getOldMethod().isPresent()) {
            return Optional.empty();
        }
        JApiMethod jApiMethod = (JApiMethod) jApiCompatibility;

```Python hl_lines="1  4"
{!../../docs_src/python_types/tutorial009.py!}
```

Sử dụng `Optional[str]` thay cho `str` sẽ cho phép trình soạn thảo giúp bạn phát hiện các lỗi mà bạn có thể gặp như một giá trị luôn là một `str`, trong khi thực tế nó rất có thể là `None`.

from typing import Optional

from fastapi import FastAPI
from fastapi.params import Param
from fastapi.testclient import TestClient

app = FastAPI()


@app.get("/items/")
def read_items(q: Optional[str] = Param(default=None)):  # type: ignore
    return {"q": q}


client = TestClient(app)


def test_default_param_query_none():
    response = client.get("/items/")
    assert response.status_code == 200, response.text

     * @param result Outcome of the current Maven build.
     * @return A {@link BuildResumptionData} instance or {@link Optional#empty()} if resuming the build is not possible.
     */
    Optional<BuildResumptionData> determineBuildResumptionData(MavenExecutionResult result);

                 TF_Message(first_bad_status.get()));
  }
}

absl::optional<std::vector<std::unique_ptr<ParallelTensor>>>
ParallelDevice::Join(
    const std::vector<PartialTensorShape>& expected_output_shapes,
    TF_Status* status) const {
  absl::optional<std::vector<std::unique_ptr<ParallelTensor>>> result;
  // Compute per-device per-output tensors

            if (executionEvent.getType() == ExecutionEvent.Type.SessionEnded) {
                usedTypes.clear();
            }
        }
    }

    @Override
    public Optional<Type> lookup(String id) {
        return Optional.of(require(id));
    }

    @Override
    @Nonnull
    public Type require(String id) {
        nonNull(id, "id");
        return usedTypes.computeIfAbsent(id, i -> {