* Updates the value currently associated with {@code key} by combining it with {@code x} via the
   * specified accumulator function, returning the new value. The previous value associated with
   * {@code key} (or zero, if there is none) is passed as the first argument to {@code
   * accumulatorFunction}, and {@code x} is passed as the second argument.
   *
   * @since 21.0
   */
  @CanIgnoreReturnValue

              <outputFilename>maven-skinny-bom.xml</outputFilename>
              <reactorDependencies>REACTOR</reactorDependencies>
              <transitiveDependencies>NONE</transitiveDependencies>
              <usePropertiesForVersion>true</usePropertiesForVersion>
              <attach>true</attach>
            </configuration>
          </execution>
          <execution>

///

## Optional File Upload { #optional-file-upload }

You can make a file optional by using standard type annotations and setting a default value of `None`:

{* ../../docs_src/request_files/tutorial001_02_an_py310.py hl[9,17] *}

## `UploadFile` with Additional Metadata { #uploadfile-with-additional-metadata }

/// note

- 请注意，您必须直接使用 `FileResponse` 返回图像。

///

/// info

- 除非在 `responses` 参数中明确指定不同的媒体类型，否则**FastAPI**将假定响应与主响应类具有相同的媒体类型（默认为` application/json` ）。
- 但是如果您指定了一个自定义响应类，并将 `None `作为其媒体类型，**FastAPI**将使用 `application/json` 作为具有关联模型的任何其他响应。

///

## 组合信息
您还可以联合接收来自多个位置的响应信息，包括 `response_model `、 `status_code` 和 `responses `参数。

Isso não é uma limitação do **FastAPI**, é parte do protocolo HTTP.

///

## Upload de Arquivo Opcional

Você pode tornar um arquivo opcional usando anotações de tipo padrão e definindo um valor padrão de `None`:

{* ../../docs_src/request_files/tutorial001_02_an_py310.py hl[9,17] *}

## `UploadFile` com Metadados Adicionais

Você também pode usar `File()` com `UploadFile`, por exemplo, para definir metadados adicionais:

```

/// tip

آرگومان دوم <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> مقدار پیش‌فرضیه که برمی‌گردونه.

اگه ندی، به‌صورت پیش‌فرض `None` هست، اینجا ما `"World"` رو به‌عنوان مقدار پیش‌فرض گذاشتیم.

///

بعد می‌تونی اون برنامه پایتون رو صدا کنی:

//// tab | لینوکس، مک‌اواس، ویندوز بش

<div class="termy">

```console

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Optional[str] = None):
    return {"item_id": item_id, "q": q}
```

* Vous devriez maintenant avoir une structure de répertoire telle que :

```
.
├── app
│   └── main.py
└── Dockerfile
```

  SUBSET_VIEW,
  DESCENDING_VIEW,

  /**
   * For documenting collections that support no optional features, such as {@link
   * java.util.Collections#emptySet}
   */
  NONE;

  private final Set<Feature<? super Collection>> implied;

  CollectionFeature(Feature<? super Collection>... implied) {
    this.implied = copyToSet(implied);
  }

  @Override

     * simply be rethrown. The default implementation returns <code>null</code>.
     * @return the authentication credentials or null if none available
     */
    protected NtlmPasswordAuthenticator getNtlmPasswordAuthentication() {
        return null;
    }

    val cookieBuilder =
      Cookie
        .Builder()
        .name("a")
        .value("b")
        .domain("example.com")
        .sameSite("None")

    val cookie = cookieBuilder.build()
    assertThat(cookie.sameSite).isEqualTo("None")
  }

  @Test fun equalsAndHashCode() {
    val cookieStrings =
      Arrays.asList(
        "a=b; Path=/c; Domain=example.com; Max-Age=5; Secure; HttpOnly",