"responses": {
                            "200": {
                                "description": "Successful Response",
                                "content": {"application/json": {"schema": {}}},
                            },
                            "422": {
                                "description": "Validation Error",
                                "content": {

        // Test creating new element
        Element description = DomUtils.updateOrCreateChildElement(root, "description", "Test Description");
        assertNotNull(description, "Should return created element");

        xmlOutput = DomUtils.toXml(doc);
        assertTrue(xmlOutput.contains("<description>Test Description</description>"), "Should contain new description");

        // Verify element ordering is maintained

    response = client.put(
        "/items/5",
        json={"description": "A very nice Item"},
    )
    assert response.status_code == 422, response.text
    assert response.json() == {
        "detail": [
            {
                "loc": ["body", "name"],
                "input": {"description": "A very nice Item"},
                "msg": "Field required",
                "type": "missing",

    model: HTTPBaseModel

    def __init__(
        self,
        *,
        scheme: str,
        scheme_name: str | None = None,
        description: str | None = None,
        auto_error: bool = True,
    ):
        self.model = HTTPBaseModel(scheme=scheme, description=description)
        self.scheme_name = scheme_name or self.__class__.__name__
        self.auto_error = auto_error

      <superClass>TrackableBase</superClass>
      <description>
        The {@code &lt;toolchains&gt;} element is the root of the descriptor.
        The following table lists all the possible child elements.
      </description>
      <version>1.0.0+</version>
      <fields>
        <field>
          <name>toolchains</name>
          <version>1.0.0+</version>
          <description>The toolchain instance definition.</description>

{* ../../docs_src/separate_openapi_schemas/tutorial001_py310.py ln[1:15] hl[14] *}

...then the `description` field will **not be required**. Because it has a default value of `None`.

### Input Model in Docs { #input-model-in-docs }

You can confirm that in the docs, the `description` field doesn't have a **red asterisk**, it's not marked as required:

<div class="screenshot">

在 OpenAPI 中，描述這種情況的方式是將該欄位標記為必填，因為它一定存在。

因此，同一個模型的 JSON Schema 會依用於輸入或輸出而不同：

- 用於輸入時，`description` 不是必填
- 用於輸出時，`description` 是必填（且可能為 `None`，在 JSON 中為 `null`）

### 文件中的輸出模型 { #model-for-output-in-docs }

你也可以在文件中檢視輸出模型，`name` 與 `description` 都以紅色星號標示為必填：

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image03.png">
</div>

### 输入用的模型 { #model-for-input }

如果你像下面这样把该模型用作输入：

{* ../../docs_src/separate_openapi_schemas/tutorial001_py310.py ln[1:15] hl[14] *}

...那么 `description` 字段将**不是必填项**，因为它的默认值是 `None`。

### 文档中的输入模型 { #input-model-in-docs }

你可以在文档中确认，`description` 字段没有**红色星号**，也就是未被标记为必填：

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image01.png">
</div>

### 输出用的模型 { #model-for-output }

from pydantic import BaseModel

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None


items = [
    Item(name="Plumbus", description="A multi-purpose household device."),
    Item(name="Portal Gun", description="A portal opening device."),
    Item(name="Meeseeks Box", description="A box that summons a Meeseeks."),
]


@app.get("/items/stream")

                            "title": "InvoiceEvent",
                            "required": ["description", "paid"],
                            "type": "object",
                            "properties": {
                                "description": {
                                    "title": "Description",
                                    "type": "string",
                                },