* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.
    * If it is not, the client will see a useful, clear error.
* 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.

        .header("Upgrade", "websocket")
        .header("Host", "square.com")
        .header("TE", "gzip")
        .build()
    val expected =
      headerEntries(
        ":method",
        "GET",
        ":path",
        "/",
        ":authority",
        "square.com",
        ":scheme",
        "http",
      )
    assertThat(http2HeadersList(request)).isEqualTo(expected)
  }

        new AtomicReference<WeakReference<?>>(
            (WeakReference<?>) sepFwrCons.newInstance(sepStopwatchA.get(), sepFrqA.get()));
    assertThat(sepStopwatchA.get()).isNotNull();
    // Clear all references to the Stopwatch and wait for it to be gc'd.
    sepStopwatchA.set(null);
    GcFinalization.awaitClear(sepStopwatchRef.get());
    // Return a weak reference to the parallel ClassLoader. This is the reference that should

        if (record == null) {
            projectRealm = classRealmManager.createProjectRealm(model, toAetherArtifacts(publicArtifacts));

            Set<String> exclusions = new LinkedHashSet<>();

            for (ClassRealm extensionRealm : extensionRealms) {
                List<String> excludes = exportedArtifacts.get(extensionRealm);

    private final ImmutableList<E> list;

    Itr(ImmutableList<E> list, int index) {
      super(list.size(), index);
      this.list = list;
    }

    @Override
    protected E get(int index) {
      return list.get(index);
    }
  }

  @Override
  public int indexOf(@Nullable Object object) {
    return (object == null) ? -1 : Lists.indexOfImpl(this, object);
  }

  @Override

    * 数据库模型
    * ......以及更多其他类型
* 自动生成的交互式 API 文档，包括两种可选的用户界面：
    * Swagger UI
    * ReDoc

---

回到前面的代码示例，**FastAPI** 将会：

* 校验 `GET` 和 `PUT` 请求的路径中是否含有 `item_id`。
* 校验 `GET` 和 `PUT` 请求中的 `item_id` 是否为 `int` 类型。
    * 如果不是，客户端将会收到清晰有用的错误信息。
* 检查 `GET` 请求中是否有命名为 `q` 的可选查询参数（比如 `http://127.0.0.1:8000/items/foo?q=somequery`）。
    * 因为 `q` 被声明为 `= None`，所以它是可选的。
    * 如果没有 `None` 它将会是必需的 (如 `PUT` 例子中的请求体)。

    Predicate<Throwable> predicate = INSTANCE_OF.get(expectedThrowable);
    if (predicate == null) {
      throw new IllegalArgumentException(
          expectedThrowable
              + " is not yet supported by ReflectionFreeAssertThrows. Add an entry for it in the"
              + " map in that class.");
    }
    Object result;
    try {
      result = supplier.get();
    } catch (Throwable t) {

    public void warnAboutDeprecatedOptions(ParserRequest request, Consumer<String> printWriter) {}

    @Override
    public void displayHelp(ParserRequest request, Consumer<String> printWriter) {
        options.get(0).displayHelp(request, printWriter);
    }

    protected <T> Optional<T> returnFirstPresentOrEmpty(Function<O, Optional<T>> getter) {
        for (O option : options) {
            Optional<T> o = getter.apply(option);

                    PluginManagement pluginMgmt = (PluginManagement) context.get(PLUGIN_MANAGEMENT);
                    if (pluginMgmt != null) {
                        for (Plugin managedPlugin : pluginMgmt.getPlugins()) {
                            Object key = getPluginKey(managedPlugin);
                            Plugin addedPlugin = added.get(key);
                            if (addedPlugin != null) {

            if (matcher.matches()) {
                return entry.getValue();
            }
        }
        return null;
    }

    /**
     * Sets the initialization parameter map for all clients.
     * @param params The map of parameters.
     */
    public void setInitParameterMap(final Map<String, Object> params) {
        if (params != null) {