<img src="/img/tutorial/body-nested-models/image01.png">

You couldn't get this kind of editor support if you were working directly with `dict` instead of Pydantic models.

But you don't have to worry about them either, incoming dicts are converted automatically and your output is converted automatically to JSON too.

## Bodies of arbitrary `dict`s

### 💯

* 1️⃣0️⃣0️⃣ 💯 <abbr title="The amount of code that is automatically tested">💯 💰</abbr>.
* 1️⃣0️⃣0️⃣ 💯 <abbr title="Python type annotations, with this your editor and external tools can give you better support">🆎 ✍</abbr> 📟 🧢.
* ⚙️ 🏭 🈸.

## 💃 ⚒

**FastAPI** 🍕 🔗 ⏮️ (&amp; ⚓️ 🔛) <a href="https://www.starlette.io/" class="external-link" target="_blank"><strong>💃</strong></a>. , 🙆 🌖 💃 📟 👆 ✔️, 🔜 👷.

    Feel free to skip this.

    Peewee is not recommended with FastAPI as it doesn't play well with anything async Python. There are several better alternatives.

!!! info
    These docs assume Pydantic v1.

    Because Pewee doesn't play well with anything async and there are better alternatives, I won't update these docs for Pydantic v2, they are kept for now only for historical purposes.

Or it might be the case that you just prefer to take other courses because they adapt better to your learning style.

Some course providers ✨ [**sponsor FastAPI**](../help-fastapi.md#sponsor-the-author){.internal-link target=_blank} ✨, this ensures the continued and healthy **development** of FastAPI and its **ecosystem**.

{!../../../docs_src/response_headers/tutorial002.py!}
```

And then you can return any object you need, as you normally would (a `dict`, a database model, etc).

And if you declared a `response_model`, it will still be used to filter and convert the object you returned.

### Is concurrency better than parallelism?

Nope! That's not the moral of the story.

Concurrency is different than parallelism. And it is better on **specific** scenarios that involve a lot of waiting. Because of that, it generally is a lot better than parallelism for web application development. But not for everything.

```json
{"message": "Hello World"}
```

...this response will return:

```json
{
  "message": "Hello World"
}
```

Of course, you will probably find much better ways to take advantage of this than formatting JSON. 😉

## Default response class

When creating a **FastAPI** class instance or an `APIRouter` you can specify which response class to use by default.

Nach einer Woche läuft der Token ab und der Benutzer wird nicht autorisiert und muss sich erneut anmelden, um einen neuen Token zu erhalten. Und wenn der Benutzer (oder ein Dritter) versuchen würde, den Token zu ändern, um das Ablaufdatum zu ändern, würden Sie das entdecken, weil die Signaturen nicht übereinstimmen würden.

OAuth2 with scopes is the mechanism used by many big authentication providers, like Facebook, Google, GitHub, Microsoft, Twitter, etc. They use it to provide specific permissions to users and applications.

Every time you "log in with" Facebook, Google, GitHub, Microsoft, Twitter, that application is using OAuth2 with scopes.

    return [pet1, pet2]


client = TestClient(app)


def test_filter_top_level_model():
    response = client.post(
        "/users", json={"email": "******@****.***", "password": "secret"}
    )
    assert response.json() == {"email": "******@****.***"}


def test_filter_second_level_model():
    response = client.get("/pets/1")
    assert response.json() == {