* Gets the installation Toolchains source.
     *
     * @return the installation Toolchains source or {@code null} if none
     */
    @Nonnull
    Optional<Source> getInstallationToolchainsSource();

    /**
     * Gets the user Toolchains source.
     *
     * @return the user Toolchains source or {@code null} if none
     */
    @Nonnull
    Optional<Source> getUserToolchainsSource();

    @Nonnull

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: str | None = Query(min_length=3)):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

from fastapi import FastAPI

app = FastAPI(docs_url="/documentation", redoc_url=None)


@app.get("/items/")
async def read_items():

```

這表示 `item` 可以是 `int` 或 `str`。

#### 可能為 `None` { #possibly-none }

你可以宣告某個值可以是某個型別（例如 `str`），但它也可能是 `None`。

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

使用 `str | None` 而不是單純的 `str`，可以讓編輯器幫你偵測錯誤，例如你以為某個值一定是 `str`，但它其實也可能是 `None`。

### 類別作為型別 { #classes-as-types }

你也可以用類別來宣告變數的型別。

`PUT`은 기존 데이터를 **대체**해야 하는 데이터를 받는 데 사용합니다.

### 대체 시 주의사항 { #warning-about-replacing }

즉, `PUT`으로 항목 `bar`를 업데이트하면서 다음과 같은 body를 보낸다면:

```Python
{
    "name": "Barz",
    "price": 3,
    "description": None,
}
```

이미 저장된 속성 `"tax": 20.2`가 포함되어 있지 않기 때문에, 입력 모델은 `"tax": 10.5`라는 기본값을 사용하게 됩니다.

그리고 데이터는 그 “새로운” `tax` 값 `10.5`로 저장됩니다.

## `PATCH`로 부분 업데이트하기 { #partial-updates-with-patch }

     * {@return the identifier of the artifact}.
     */
    @Nonnull
    String getArtifactId();

    /**
     * Returns the classifier of the artifact.
     *
     * @return the classifier or an empty string if none, never {@code null}
     */
    @Nonnull
    String getClassifier();

    /**
     * {@return the specific version, range of versions, or meta-version of the artifact}.

<li>Current HEAD Piper Changelist, if any: cl/${KOKORO_PIPER_CHANGELIST:-not available}</li>
<li>Pull Request Number, if any: ${KOKORO_GITHUB_PULL_REQUEST_NUMBER_tensorflow:- none}</li>
<li>Pull Request Link, if any: <a href="$KOKORO_GITHUB_PULL_REQUEST_URL_tensorflow">${KOKORO_GITHUB_PULL_REQUEST_URL_tensorflow:-none}</a></li>
<li>Commit: $KOKORO_GIT_COMMIT_tensorflow</li>
</ul>
<h2>Googlers-Only Links</h2>
<ul>

import orjson
from fastapi import FastAPI, Response

app = FastAPI()


class CustomORJSONResponse(Response):
    media_type = "application/json"

    def render(self, content: Any) -> bytes:
        assert orjson is not None, "orjson must be installed"
        return orjson.dumps(content, option=orjson.OPT_INDENT_2)


@app.get("/", response_class=CustomORJSONResponse)
async def main():

def get_client():
    app = FastAPI()
    with pytest.warns(FastAPIDeprecationWarning):

        @app.get("/items/")
        async def read_items(
            q: Annotated[str | None, Query(regex="^fixedquery$")] = None,
        ):
            if q:
                return f"Hello {q}"
            else:
                return "Hello World"

    client = TestClient(app)
    return client


@needs_py310

from typing import Annotated

from fastapi import FastAPI, Query

app = FastAPI()


@app.get("/items/")
async def read_items(q: Annotated[str | None, Query(min_length=3)]):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})