And `items.router` contains the `APIRouter` inside of the file `app/routers/items.py`.

///

With `app.include_router()` we can add each `APIRouter` to the main `FastAPI` application.

It will include all the routes from that router as part of it.

/// note | Technical Details

It will actually internally create a *path operation* for each *path operation* that was declared in the `APIRouter`.

    @app.post(
        "/",
        response_model=list[Item],
        responses={404: {"model": list[Message]}},
        generate_unique_id_function=custom_generate_unique_id3,
        callbacks=callback_router.routes,
    )
    def post_root(item1: Item, item2: Item):
        return item1, item2  # pragma: nocover

    @app.post(
        "/tocallback",
        response_model=list[Item],

		return matches[1]
	}
	return "unknown"
}

func methodNotAllowedHandler(api string) func(w http.ResponseWriter, r *http.Request) {
	return errorResponseHandler
}

// If none of the http routes match respond with appropriate errors
func errorResponseHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == http.MethodOptions {
		return
	}

## FastAPI 特性

**FastAPI** 提供了以下内容：

### 基于开放标准


* 用于创建 API 的 <a href="https://github.com/OAI/OpenAPI-Specification" class="external-link" target="_blank"><strong>OpenAPI</strong></a> 包含了<abbr title="也被叫做: endpoints, routes">路径</abbr><abbr title="也叫做HTTP方法, 例如 POST, GET, PUT, DELETE">操作</abbr>，请求参数，请求体，安全性等的声明。

   * Optional<T>}. Casting either of the above example {@code Optional} instances to {@code
   * Optional<Number>} (where {@code Number} is the desired output type) solves the problem:
   *
   * {@snippet :
   * Optional<Number> optionalInt = (Optional) getSomeOptionalInt();
   * Number value = optionalInt.or(0.5); // fine
   *

labels.facet_timestamp_1day=Within 24 hours
labels.facet_timestamp_1week=Within a week
labels.facet_timestamp_1month=Within a month
labels.facet_timestamp_1year=Within a year
labels.facet_timestamp_3month=Within 3 months
labels.facet_timestamp_6month=Within 6 months
labels.facet_timestamp_2year=Within 2 years
labels.facet_timestamp_3year=Within 3 years
labels.facet_contentLength_title=Size
labels.facet_contentLength_10k=  - 10KB

## FastAPI 特性

**FastAPI** 提供了以下内容：

### 建立在開放標準的基礎上

* 使用 <a href="https://github.com/OAI/OpenAPI-Specification" class="external-link" target="_blank"><strong>OpenAPI</strong></a> 來建立 API，包含<abbr title="path，也被叫做: endpoints, routes">路徑</abbr><abbr title="也叫做 HTTP 方法，例如 POST, GET, PUT, DELETE">操作</abbr>、參數、請求內文、安全性等聲明。
* 使用 <a href="https://json-schema.org/" class="external-link" target="_blank"><strong>JSON Schema</strong></a>（因為 OpenAPI 本身就是基於 JSON Schema）自動生成資料模型文件。

                terms_of_service=self.terms_of_service,
                contact=self.contact,
                license_info=self.license_info,
                routes=self.routes,
                webhooks=self.webhooks.routes,
                tags=self.openapi_tags,
                servers=self.servers,
                separate_input_output_schemas=self.separate_input_output_schemas,

  fun disconnectRequestHalfway() {
    server.enqueue(MockResponse().setSocketPolicy(SocketPolicy.DISCONNECT_DURING_REQUEST_BODY))
    // Limit the size of the request body that the server holds in memory to an arbitrary
    // 3.5 MBytes so this test can pass on devices with little memory.
    server.bodyLimit = 7 * 512 * 1024
    val connection = server.url("/").toUrl().openConnection() as HttpURLConnection
    connection.setRequestMethod("POST")

// The bytes written matches the number of remaining bytes in the current file.
//
// If the current file is sparse and w is an io.WriteSeeker,
// then writeTo uses Seek to skip past holes defined in Header.SparseHoles,
// assuming that skipped regions are filled with NULs.
// This always writes the last byte to ensure w is the right size.
//
// TODO(dsnet): Re-export this when adding sparse file support.