* </ul>
 *
 * To force selection of our fallback strategies we load {@link AbstractFuture} (and all of {@code
 * com.google.common.util.concurrent}) in degenerate class loaders which make certain platform
 * classes unavailable. Then we construct a test suite so we can run the normal AbstractFutureTest
 * test methods in these degenerate classloaders.
 */

 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AggregateFutureState} (and all of
 * {@code com.google.common.util.concurrent}) in degenerate class loaders which make certain
 * platform classes unavailable. Then we construct a test suite so we can run the normal FuturesTest
 * test methods in these degenerate classloaders.
 */

 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AggregateFutureState} (and all of
 * {@code com.google.common.util.concurrent}) in degenerate class loaders which make certain
 * platform classes unavailable. Then we construct a test suite so we can run the normal FuturesTest
 * test methods in these degenerate classloaders.
 */

 * </ul>
 *
 * To force selection of our fallback strategies we load {@link AbstractFuture} (and all of {@code
 * com.google.common.util.concurrent}) in degenerate class loaders which make certain platform
 * classes unavailable. Then we construct a test suite so we can run the normal AbstractFutureTest
 * test methods in these degenerate classloaders.
 */

   *     used as a {@code Function} only with cache loaders that throw only unchecked exceptions.)
   */
  @Deprecated
  @Override
  V apply(K key);

  /**
   * Loads a new value for {@code key}, possibly asynchronously. While the new value is loading the
   * previous value (if any) will continue to be returned by {@code get(key)} unless it is evicted.

   *     used as a {@code Function} only with cache loaders that throw only unchecked exceptions.)
   */
  @Deprecated
  @Override
  V apply(K key);

  /**
   * Loads a new value for {@code key}, possibly asynchronously. While the new value is loading the
   * previous value (if any) will continue to be returned by {@code get(key)} unless it is evicted.

   * {@linkplain Thread#getContextClassLoader() context class loader}. In simple environments, the
   * context class loader will find resources from the class path. In environments where different
   * threads can have different class loaders, for example app servers, the context class loader
   * will typically have been set to an appropriate loader for the current thread.
   *

 *
 * <p>This class can't depend on other Guava code. If we were to load this class in the same class
 * loader as the rest of Guava, this thread would keep an indirect strong reference to the class
 * loader and prevent it from being garbage collected. This poses a problem for environments where

 *
 * <p>This class can't depend on other Guava code. If we were to load this class in the same class
 * loader as the rest of Guava, this thread would keep an indirect strong reference to the class
 * loader and prevent it from being garbage collected. This poses a problem for environments where

# 响应头

## 使用 `Response` 参数

你可以在你的*路径操作函数*中声明一个`Response`类型的参数（就像你可以为cookies做的那样）。

然后你可以在这个*临时*响应对象中设置头部。
```Python hl_lines="1  7-8"
{!../../../docs_src/response_headers/tutorial002.py!}
```

然后你可以像平常一样返回任何你需要的对象（例如一个`dict`或者一个数据库模型）。如果你声明了一个`response_model`，它仍然会被用来过滤和转换你返回的对象。

**FastAPI**将使用这个临时响应来提取头部（也包括cookies和状态码），并将它们放入包含你返回的值的最终响应中，该响应由任何`response_model`过滤。

你也可以在依赖项中声明`Response`参数，并在其中设置头部（和cookies）。

## 直接返回 `Response`