//   must be either listed in `inputs` or must come from another node in
//   the body. In particular, it is an error to have a control edge going from
//   a node outside of the body into a node in the body. This applies to control
//   edges going from nodes referenced in `inputs` to nodes in the body when
//   the former nodes are not in the body (automatically skipped or not

## 响应模型编码参数

你的响应模型可以具有默认值，例如：

```Python hl_lines="11  13-14"
{!../../docs_src/response_model/tutorial004.py!}
```

* `description: Union[str, None] = None` 具有默认值 `None`。
* `tax: float = 10.5` 具有默认值 `10.5`.
* `tags: List[str] = []` 具有一个空列表作为默认值： `[]`.

但如果它们并没有存储实际的值，你可能想从结果中忽略它们的默认值。

举个例子，当你在 NoSQL 数据库中保存了具有许多可选属性的模型，但你又不想发送充满默认值的很长的 JSON 响应。

[kubernetes-node-linux-arm.tar.gz](https://dl.k8s.io/v1.6.13/kubernetes-node-linux-arm.tar.gz) | `9d0433621021bca490e8a04eb96e47402d3f8e3d47762590b83be6a595d29b16`
[kubernetes-node-linux-ppc64le.tar.gz](https://dl.k8s.io/v1.6.13/kubernetes-node-linux-ppc64le.tar.gz) | `438f0e05d29e371c028e73b28c31e3b13dc1decd0780557e0231d96de871b419`

 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//

    protected void parseTextContent(final Node node, final StringBuilder buf) {
        if (node.hasChildNodes()) {
            final NodeList nodeList = node.getChildNodes();
            for (int i = 0; i < nodeList.getLength(); i++) {
                final Node childNode = nodeList.item(i);
                parseTextContent(childNode, buf);
            }
        } else if (node.getNodeType() == Node.TEXT_NODE) {

* Wenn der Parameter vom Typ eines **Pydantic-Modells** ist, wird er als Request**body** interpretiert.

/// note | "Hinweis"

FastAPI weiß, dass der Wert von `q` nicht erforderlich ist, wegen des definierten Defaultwertes `= None`

Das `Union` in `Union[str, None]` wird von FastAPI nicht verwendet, aber es erlaubt Ihrem Editor, Sie besser zu unterstützen und Fehler zu erkennen.

///

## Ohne Pydantic

* Se o parâmetro é declarado como um **modelo Pydantic**, será interpretado como o **corpo** da requisição.

/// note | "Observação"

O FastAPI saberá que o valor de `q` não é obrigatório por causa do valor padrão `= None`.

O `Union` em `Union[str, None]` não é utilizado pelo FastAPI, mas permite ao seu editor de texto lhe dar um suporte melhor e detectar erros.

///

## Sem o Pydantic

[kubernetes-node-linux-arm64.tar.gz](https://dl.k8s.io/v1.9.10/kubernetes-node-linux-arm64.tar.gz) | `8b6d61316e99c17d51ffd966c26d2034960947968a5a6840e547a1966a087ad7`
[kubernetes-node-linux-ppc64le.tar.gz](https://dl.k8s.io/v1.9.10/kubernetes-node-linux-ppc64le.tar.gz) | `471d3a21f9bd8e8a7f03f8d225c4a72d7305f888102556e0ba29e5ec86dc763e`