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

    }

    public void setName_Equal(String name) {
        setName_Term(name, null);
    }

    public void setName_Equal(String name, ConditionOptionCall<TermQueryBuilder> opLambda) {
        setName_Term(name, opLambda);
    }

    public void setName_Term(String name) {
        setName_Term(name, null);
    }

    public void setName_Term(String name, ConditionOptionCall<TermQueryBuilder> opLambda) {

        SmbFile listDir = new SmbFile(baseUrl + "shared/listdir_" + timestamp + "/", listContext);
        String[] names = listDir.list();
        assertNotNull(names, "List should not be null");
        assertEquals(3, names.length, "Should list 3 items");

        List<String> nameList = List.of(names);
        assertTrue(nameList.contains("file1.txt"), "Should contain file1.txt");

#     }
# }
#
# *The line that starts with '#' means comment-out.
#
map:{
    # your service name, camel case, initial uncapitalised
    ; serviceName = fess

    # package for your domain name, e.g. com.example
    ; domainPackage = org.codelibs.fess

    # keywords for environment properties, same as directory name
    ; environmentList = list:{}

    # environment dispatch by lasta.env of system property?

)


fake_items_db = {"plumbus": {"name": "Plumbus"}, "gun": {"name": "Portal Gun"}}


@router.get("/")
async def read_items():
    return fake_items_db


@router.get("/{item_id}")
async def read_item(item_id: str):
    if item_id not in fake_items_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return {"name": fake_items_db[item_id]["name"], "item_id": item_id}


@router.put(

from fastapi.testclient import TestClient
from pydantic import BaseModel


class Item(BaseModel):
    name: str
    price: float


app = FastAPI()


@app.get("/items/stream-invalid")
async def stream_items_invalid() -> AsyncIterable[Item]:
    yield {"name": "valid", "price": 1.0}
    yield {"name": "invalid", "price": "not-a-number"}


@app.get("/items/stream-invalid-sync")

* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`) for `GET` requests.
    * As the `q` parameter is declared with `= None`, it is optional.
    * Without the `None` it would be required (as is the body in the case with `PUT`).
* For `PUT` requests to `/items/{item_id}`, read the body as JSON:
    * Check that it has a required attribute `name` that should be a `str`.

kind: CiliumNetworkPolicy
apiVersion: cilium.io/v2
metadata:
  name: {{ template "minio.fullname" . }}
  labels:
    app: {{ template "minio.name" . }}
    chart: {{ template "minio.chart" . }}
    release: {{ .Release.Name }}
    heritage: {{ .Release.Service }}
spec:
  endpointSelector:
    matchLabels:
      app: {{ template "minio.name" . }}
      release: {{ .Release.Name }}
  ingress:
  - toPorts:
    - ports:

                                                                                <input type="hidden" name="name"
                                                                                       value="${f:h(artifact.name)}">
                                                                                <input type="hidden" name="version"

	for _, object := range resp.Objects {
		if object.Name == "" {
			continue
		}
		// Cache checks for the same object
		if metadata != nil && lastObjMetaName != object.Name {
			tagErr = metadata(object.Name, policy.GetObjectTaggingAction)
			metaErr = metadata(object.Name, policy.GetObjectAction)
			lastObjMetaName = object.Name
		}
		content := ObjectVersion{}