```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`.

`Optional[Something]` là một cách viết ngắn gọn của `Union[Something, None]`, chúng là tương đương nhau.

Điều này cũng có nghĩa là trong Python 3.10, bạn có thể sử dụng `Something | None`:

### Response Elements

XML response for this API is similar to [AWS STS AssumeRoleWithWebIdentity](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRoleWithWebIdentity.html#API_AssumeRoleWithWebIdentity_ResponseElements)

### Errors

XML error response for this API is similar to [AWS STS AssumeRoleWithWebIdentity](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRoleWithWebIdentity.html#API_AssumeRoleWithWebIdentity_Errors)

| Parameter | Type | Description |
|------------|------|-------------|
| `title` | `str` | The title of the API. |
| `summary` | `str` | A short summary of the API. <small>Available since OpenAPI 3.1.0, FastAPI 0.99.0.</small> |
| `description` | `str` | A short description of the API. It can use Markdown. |

        @Override
        Optional<String> chop(String str) {
          return i.chop(str).or(you.chop(str));
        }
      };
    }

    abstract Optional<String> chop(String str);

    static Chopper suffix(String suffix) {
      return new Chopper() {
        @Override
        Optional<String> chop(String str) {
          if (str.endsWith(suffix)) {

同様に、このデータベースはPydanticモデル（属性を持つオブジェクト）を受け取らず、`dict`だけを受け取ります。

そのために`jsonable_encoder`を使用することができます。

Pydanticモデルのようなオブジェクトを受け取り、JSON互換版を返します:

{* ../../docs_src/encoder/tutorial001.py hl[5,22] *}

この例では、Pydanticモデルを`dict`に、`datetime`を`str`に変換します。

	sr.lock.Lock()
	defer sr.lock.Unlock()
	srs, ok := sr.M[dID]
	if !ok {
		srs = &SRStatus{
			XferRateLrg: newXferStats(),
			XferRateSml: newXferStats(),
		}
	}
	srs.Endpoint = st.Endpoint
	srs.Secure = st.Secure
	switch {
	case st.Completed:
		srs.ReplicatedSize += st.TransferSize
		srs.ReplicatedCount++
		if st.TransferDuration > 0 {
			srs.Latency.update(st.TransferSize, st.TransferDuration)

    * Wird in Requests und Responses als `str` dargestellt.
* `datetime.datetime`:
    * Ein Python-`datetime.datetime`.
    * Wird in Requests und Responses als `str` im ISO 8601-Format dargestellt, etwa: `2008-09-15T15:53:00+05:00`.
* `datetime.date`:
    * Python-`datetime.date`.
    * Wird in Requests und Responses als `str` im ISO 8601-Format dargestellt, etwa: `2008-09-15`.
* `datetime.time`:

     */
    @Test
    void toStringIncludesClassName() {
        TransWaitNamedPipeResponse resp = new TransWaitNamedPipeResponse();
        String str = resp.toString();
        assertNotNull(str, "toString should not return null");
        assertTrue(str.startsWith("TransWaitNamedPipeResponse["), "toString should begin with class name");
    }

    /**

The validity duration of the generated STS credentials is the minimum of the `DurationSeconds` parameter (if passed) and the validity duration returned by the Identity Management Plugin.

## API Response

XML response for this API is similar to [AWS STS AssumeRoleWithWebIdentity](https://docs.aws.amazon.com/STS/latest/APIReference/API_AssumeRoleWithWebIdentity.html#API_AssumeRoleWithWebIdentity_ResponseElements)

	  "Resource": ["arn:aws:s3:::mybucket/${aws:username}/*"]
	}
  ]
}
```

If the user is authenticating using an STS credential which was authorized from OpenID connect we allow all `jwt:*` variables specified in the JWT specification, custom `jwt:*` or extensions are not supported. List of policy variables for OpenID based STS.

- `jwt:sub`
- `jwt:iss`
- `jwt:aud`
- `jwt:jti`
- `jwt:upn`
- `jwt:name`
- `jwt:groups`