これを行うには、`return`の代わりに`yield`を使い、その後に追加のステップを書きます。

/// tip | "豆知識"

`yield`は必ず一度だけ使用するようにしてください。

///

/// info | "情報"

これを動作させるには、**Python 3.7** 以上を使用するか、**Python 3.6** では"backports"をインストールする必要があります:

```
pip install async-exit-stack async-generator
```

您还可以使用[SQLite Viewer](https://inloop.github.io/sqlite-viewer/)或[ExtendsClass](https://extendsclass.com/sqlite-browser.html)等在线 SQLite 浏览器。

## 中间件替代数据库会话

如果你不能使用带有`yield`的依赖项——例如，如果你没有使用**Python 3.7**并且不能安装上面提到的**Python 3.6**的“backports” ——你可以使用类似的方法在“中间件”中设置会话。

“中间件”基本上是一个对每个请求都执行的函数，其中一些代码在端点函数之前执行，另一些代码在端点函数之后执行。

### 创建中间件

我们要添加的中间件（只是一个函数）将为每个请求创建一个新的 SQLAlchemy`SessionLocal`，将其添加到请求中，然后在请求完成后关闭它。

//// tab | Python 3.9+

[`jstmpllitinterp` setting](/pkg/html/template#hdr-Security_Model).
This behavior was backported to Go 1.19.8+ and Go 1.20.3+.

Go 1.21 introduced a limit on the maximum number of MIME headers and multipart
forms, controlled by the
[`multipartmaxheaders` and `multipartmaxparts` settings](/pkg/mime/multipart#hdr-Limits)
respectively.
This behavior was backported to Go 1.19.8+ and Go 1.20.3+.

   * ClassValueValidator.
   *
   * Fortunately, we get pretty good coverage "by accident": We run all these tests against the
   * *backport*, where ClassValueValidator is not present.
   */

 *
 * @author Colin Decker
 */

public class MoreFilesTest extends TestCase {

  /*
   * Note: We don't include suite() in the backport. I've lost track of whether the Android test
   * runner would run it even if we did, but part of the problem is b/230620681.
   */

  private static final FileSystem FS = FileSystems.getDefault();

     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
     * ImmutableSortedSet#orderedBy}.
     */
    /*
     * TODO(cpovirk): use Object[] instead of E[] in the mainline? (The backport is different and
     * doesn't need this suppression, but we keep it to minimize diffs.) Generally be more clear
     * about when we have an Object[] vs. a Comparable[] or other array type in internalArray? If we

     * Creates a new builder. The returned builder is equivalent to the builder generated by {@link
     * ImmutableSortedSet#orderedBy}.
     */
    /*
     * TODO(cpovirk): use Object[] instead of E[] in the mainline? (The backport is different and
     * doesn't need this suppression, but we keep it to minimize diffs.) Generally be more clear
     * about when we have an Object[] vs. a Comparable[] or other array type in internalArray? If we