test_db.unlink()
    # Import while creating the client to create the DB after starting the test session
    from docs_src.sql_databases.sql_app_py310 import alt_main

    # Ensure import side effects are re-executed
    importlib.reload(alt_main)

    with TestClient(alt_main.app) as c:
        yield c
    if test_db.is_file():  # pragma: nocover
        test_db.unlink()
    os.chdir(cwd)


@needs_py310

You don't even have to check if the token exists to return an error. You can be sure that if your function is executed, it will have a `str` in that token.

You can try it already in the interactive docs:

<img src="/img/tutorial/security/image03.png">

We are not verifying the validity of the token yet, but that's a start already.

Only the code prior to and including the `yield` statement is executed before creating a response:

```Python hl_lines="2-4"
{!../../../docs_src/dependencies/tutorial007.py!}
```

The yielded value is what is injected into *path operations* and other dependencies:

```Python hl_lines="4"
{!../../../docs_src/dependencies/tutorial007.py!}
```

The code following the `yield` statement is executed after the response has been delivered:

A "**callable**" in Python is anything that Python can "call" like a function.

So, if you have an object `something` (that might _not_ be a function) and you can "call" it (execute it) like:

```Python
something()
```

or

```Python
something(some_argument, some_keyword_argument="foo")
```

then it is a "callable".

## Classes as dependencies

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

* Então clique no botão "Execute", a interface do usuário irá se comunicar com a API, enviar os parâmetros, pegar os resultados e mostrá-los na tela:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-05-swagger-04.png)

* "Try it out" düyməsini klikləyin, bu, parametrləri doldurmağa və API ilə birbaşa əlaqə saxlamağa imkan verir:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

* Sonra "Execute" düyməsini klikləyin, istifadəçi interfeysi API ilə əlaqə quracaq, parametrləri göndərəcək, nəticələri əldə edəcək və onları ekranda göstərəcək:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-05-swagger-04.png)

* Click vào nút "Try it out", nó cho phép bạn điền những tham số và tương tác trực tiếp với API:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

* Sau khi click vào nút "Execute", giao diện người dùng sẽ giao tiếp với API của bạn bao gồm: gửi các tham số, lấy kết quả và hiển thị chúng trên màn hình:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-05-swagger-04.png)

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

* Lẹhinna tẹ bọtini "Ṣiṣe" i.e. "Execute", olùmúlò (i.e. user interface) yóò sọrọ pẹ̀lú API rẹ, yóò ṣe afiranṣẹ àwọn èròjà, pàápàá jùlọ yóò gba àwọn àbájáde yóò si ṣafihan wọn loju ìbòjú:

- "Try it out"ボタンをクリックしてください。パラメータを入力して API と直接やりとりすることができます:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

- それから、"Execute" ボタンをクリックしてください。 ユーザーインターフェースは API と通信し、パラメータを送信し、結果を取得して画面に表示します:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-05-swagger-04.png)

### 代替の API ドキュメントのアップグレード

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-04-swagger-03.png)

* Şimdi "Execute" butonuna tıklayalım, kullanıcı arayüzü API'ımız ile bağlantı kurup parametreleri gönderecek ve sonucu ekranımıza getirecek:

![Swagger UI interaction](https://fastapi.tiangolo.com/img/index/index-05-swagger-04.png)