Esse código declara um parâmetro de consulta opcional, `q`, com o tipo `str`, e então retorna esse parâmetro.

Isso é bastante simples (e não muito útil), mas irá nos ajudar a focar em como as subdependências funcionam.

## Segunda dependência, "injetável" e "dependente"

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

Let's focus on the parameters declared:

* Even though this function is a dependency ("dependable") itself, it also declares another dependency (it "depends" on something else).
    * It depends on the `query_extractor`, and assigns the value returned by it to the parameter `q`.
* It also declares an optional `last_query` cookie, as a `str`.

Vous pouvez déclarer un `response_model`, en utilisant le code HTTP par défaut `200` (ou un code personnalisé si vous en avez besoin), puis déclarer des informations supplémentaires pour cette même réponse dans `responses`, directement dans le schéma OpenAPI.

{*../../docs_src/python_types/tutorial004.py hl[2] *}

## Déclarer des types

Vous venez de voir là où les types sont généralement déclarés : dans les paramètres de fonctions.

C'est aussi ici que vous les utiliseriez avec **FastAPI**.

### Types simples

Vous pouvez déclarer tous les types  de Python, pas seulement `str`.

Comme par exemple :

* `int`
* `float`

```Python
q: str
```

à la place de :

```Python
q: Union[str, None] = None
```

Mais maintenant, on déclare `q` avec `Query`, comme ceci :

```Python
q: Union[str, None] = Query(default=None, min_length=3)
```

Donc pour déclarer une valeur comme requise tout en utilisant `Query`, il faut utiliser `...` comme premier argument :

  private final ImmutableList<Annotation> annotations;

  /**
   * An {@code AnnotatedType} instance, or {@code null} under Android VMs (possible only when using
   * the Android flavor of Guava). The field is declared with a type of {@code Object} to avoid
   * compatibility problems on Android VMs. The corresponding accessor method, however, can have the

Esse parâmetro não cria um endpoint / *path operation*, mas declara que a URL `/token` vai ser aquela que o client deve usar para obter o token. Essa informação é usada no OpenAPI, e depois na API Interativa de documentação de sistemas.

Em breve também criaremos o atual path operation.

* The user types the `username` and `password` in the frontend, and hits `Enter`.
* The frontend (running in the user's browser) sends that `username` and `password` to a specific URL in our API (declared with `tokenUrl="token"`).
* The API checks that `username` and `password`, and responds with a "token" (we haven't implemented any of this yet).

{* ../../docs_src/response_model/tutorial003_py310.py hl[24] *}

...we declared the `response_model` to be our model `UserOut`, that doesn't include the password:

{* ../../docs_src/response_model/tutorial003_py310.py hl[22] *}

So, **FastAPI** will take care of filtering out all the data that is not declared in the output model (using Pydantic).

### `response_model` or Return Type { #response-model-or-return-type }

Each "scope" is just a string (without spaces).

They are normally used to declare specific security permissions, for example:

* `users:read` or `users:write` are common examples.
* `instagram_basic` is used by Facebook / Instagram.
* `https://www.googleapis.com/auth/drive` is used by Google.

/// info

In OAuth2 a "scope" is just a string that declares a specific permission required.