STXRH R12, (R3), R8                        // 6c7c0848
	SUBW R20.UXTW<<2, R23, R19                 // f34a344b
	SUB R5.SXTW<<2, R1, R26                    // 3ac825cb
	SUB $(1923<<12), R4, R27                   // SUB $7876608, R4, R27         // 9b0c5ed1
	SUBW $(1923<<12), R4, R27                  // SUBW $7876608, R4, R27        // 9b0c5e51
	SUBW R12<<29, R7, R8                       // e8740c4b
	SUB R12<<61, R7, R8                        // e8f40ccb

    <diagram id="zB4-QXJZ7ScUzHSLnJ1i" name="Page-1">
        <mxGraphModel dx="1154" dy="780" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="1" pageScale="1" pageWidth="1920" pageHeight="1200" math="0" shadow="0" extFonts="Roboto^https://fonts.googleapis.com/css?family=Roboto|Roboto Mono, mono^https://fonts.googleapis.com/css?family=Roboto+Mono%2C+mono">
            <root>
                <mxCell id="0"/>

```

### 创建回调*路径操作*

创建回调*路径操作*也使用之前创建的 `APIRouter`。

它看起来和常规 FastAPI *路径操作*差不多：

* 声明要接收的请求体，例如，`body: InvoiceEvent`
* 还要声明要返回的响应，例如，`response_model=InvoiceEventReceived`

```Python hl_lines="17-19  22-23  29-33"
{!../../../docs_src/openapi_callbacks/tutorial001.py!}
```

回调*路径操作*与常规*路径操作*有两点主要区别：

* 它不需要任何实际的代码，因为应用不会调用这段代码。它只是用于存档*外部 API*。因此，函数的内容只需要 `pass` 就可以了

  private static final long ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x007f - 0x0000 + 1;

  // 128
  private static final long EXPECTED_ONE_BYTE_ROUNDTRIPPABLE_COUNT =
      ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS;

  // 1920 [chars 0x0080 to 0x07FF]
  private static final long TWO_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x07FF - 0x0080 + 1;

  // 18,304
  private static final long EXPECTED_TWO_BYTE_ROUNDTRIPPABLE_COUNT =

    private static final Collection<String> TRANSLATED_PATH_EXPRESSIONS;

    static {
        Collection<String> translatedPrefixes = new HashSet<>();

        // MNG-1927, MNG-2124, MNG-3355:
        // If the build section is present and the project directory is non-null, we should make
        // sure interpolation of the directories below uses translated paths.

* `swagger_css_url`: the URL where the HTML for your Swagger UI docs can get the **CSS** file. This is the custom CDN URL.

And similarly for ReDoc...

```Python hl_lines="2-6  11-19  22-24  27-33"
{!../../../docs_src/custom_docs_ui/tutorial001.py!}
```

!!! tip
    The *path operation* for `swagger_ui_redirect` is a helper for when you use OAuth2.

func stack1916() { var buf [1916]byte; use(buf[:]); C.callGoStackCheck() }
func stack1920() { var buf [1920]byte; use(buf[:]); C.callGoStackCheck() }
func stack1924() { var buf [1924]byte; use(buf[:]); C.callGoStackCheck() }
func stack1928() { var buf [1928]byte; use(buf[:]); C.callGoStackCheck() }
func stack1932() { var buf [1932]byte; use(buf[:]); C.callGoStackCheck() }

        verifyNfold(64, "Rough Consensus, and Running Code", "bb6ed30870b7f0e0");
        verifyNfold(168, "password", "59e4a8ca7c0385c3c37b3f6d2000247cb6e6bd5b3e");
        verifyNfold(192, "MASSACHVSETTS INSTITVTE OF TECHNOLOGY", "db3b0d8f0b061e603282b308a50841229ad798fab9540c1b");
        verifyNfold(168, "Q", "518a54a215a8452a518a54a215a8452a518a54a215");

И, в свою очередь, `dependency_b` нуждается в том, чтобы значение из `dependency_a` (здесь `dep_a`) было доступно для ее завершающего кода.

=== "Python 3.9+"

    ```Python hl_lines="18-19  26-27"
    {!> ../../../docs_src/dependencies/tutorial008_an_py39.py!}
    ```

=== "Python 3.6+"

    ```Python hl_lines="17-18  25-26"
    {!> ../../../docs_src/dependencies/tutorial008_an.py!}
    ```

  private static final long ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x007f - 0x0000 + 1;

  // 128
  private static final long EXPECTED_ONE_BYTE_ROUNDTRIPPABLE_COUNT =
      ONE_BYTE_ROUNDTRIPPABLE_CHARACTERS;

  // 1920 [chars 0x0080 to 0x07FF]
  private static final long TWO_BYTE_ROUNDTRIPPABLE_CHARACTERS = 0x07FF - 0x0080 + 1;

  // 18,304
  private static final long EXPECTED_TWO_BYTE_ROUNDTRIPPABLE_COUNT =