举个例子，看这段函数：

```python
from typing import Optional


def say_hi(name: Optional[str]):
    print(f"Hey {name}!")
```

参数 `name` 被定义为 `Optional[str]`，但它并不是“可选”的，你不能不传这个参数就调用函数：

```Python
say_hi()  # 哎呀，这会报错！😱
```

参数 `name` 仍然是必填的（不是“可选”），因为它没有默认值。不过，`name` 接受 `None` 作为取值：

```Python
say_hi(name=None)  # 这样可以，None 是有效的 🎉
```

好消息是，在大多数情况下，你可以直接使用 `|` 来定义类型联合：

```python

def get_authors():  # (8)
    return [  # (9)
        {
            "name": "Breaters",
            "items": [
                {
                    "name": "Island In The Moon",
                    "description": "A place to be playin' and havin' fun",
                },
                {"name": "Holy Buddies"},
            ],
        },
        {
            "name": "System of an Up",
            "items": [
                {

			}, clause.Select{
				Columns: []clause.Column{{Name: "name"}},
			}, clause.From{}},
			"SELECT `name` FROM `users`", nil,
		},
		{
			[]clause.Interface{clause.Select{
				Expression: clause.CommaExpression{
					Exprs: []clause.Expression{
						clause.NamedExpr{"?", []interface{}{clause.Column{Name: "id"}}},
						clause.NamedExpr{"?", []interface{}{clause.Column{Name: "name"}}},

      - name: 'Integration Test'
        if: matrix.java == 11
        shell: bash
        run: util/gradle_integration_tests.sh

  publish_snapshot:
    name: 'Publish snapshot'
    needs: test
    if: github.event_name == 'push' && github.repository == 'google/guava'
    runs-on: ubuntu-latest
    steps:
      - name: 'Check out repository'

        // DataOffset field (2 bytes) - should be 24 (16 header + 4 name + 4 padding)
        assertEquals(24, SMBUtil.readInt2(buffer, 10));

        // DataLength field (4 bytes) - should be 32 (lease V1 structure size)
        assertEquals(32, SMBUtil.readInt4(buffer, 12));

        // Verify context name is encoded at offset 16
        byte[] nameBytes = new byte[4];

// NestedRelationName nested relationships like `Manager__Company`
func NestedRelationName(prefix, name string) string {
	return prefix + nestedRelationSplit + name
}

// SplitNestedRelationName Split nested relationships to `[]string{"Manager","Company"}`
func SplitNestedRelationName(name string) []string {
	return strings.Split(name, nestedRelationSplit)
}

// JoinNestedRelationNames nested relationships like `Manager__Company`

    def __init__(
        self,
        location: APIKeyIn,
        name: str,
        description: str | None,
        scheme_name: str | None,
        auto_error: bool,
    ):
        self.auto_error = auto_error

        self.model: APIKey = APIKey(
            **{"in": location},  # ty: ignore[invalid-argument-type]
            name=name,
            description=description,
        )

                          const char* name) {
  unique_tensor_ptr tensor(BoolTensor(v), TF_DeleteTensor);
  return Const(tensor.get(), graph, s, name);
}

TF_Operation* ScalarConst(int32_t v, TF_Graph* graph, TF_Status* s,
                          const char* name) {
  unique_tensor_ptr tensor(Int32Tensor(v), TF_DeleteTensor);
  return Const(tensor.get(), graph, s, name);
}

from fastapi import FastAPI
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")

<div class="wrapper">
    <jsp:include page="/WEB-INF/view/common/admin/header.jsp"></jsp:include>
    <jsp:include page="/WEB-INF/view/common/admin/sidebar.jsp">
        <jsp:param name="menuCategoryType" value="crawl"/>
        <jsp:param name="menuType" value="requestHeader"/>
    </jsp:include>
    <main class="content-wrapper">
        <div class="content-header">
            <div class="container-fluid">