async def __call__(self, request: Request) -> Optional[str]:
        api_key = request.query_params.get(self.model.name)
        if not api_key:
            if self.auto_error:
                raise HTTPException(
                    status_code=HTTP_403_FORBIDDEN, detail="Not authenticated"
                )
            else:
                return None
        return api_key

class DictablePet(Pet):
    def __iter__(self):
        return ((k, v) for k, v in self.__dict__.items())


class Unserializable:
    def __iter__(self):
        raise NotImplementedError()

    @property
    def __dict__(self):
        raise NotImplementedError()


class RoleEnum(Enum):
    admin = "admin"
    normal = "normal"


class ModelWithConfig(BaseModel):
    role: Optional[RoleEnum] = None

{!../../../docs_src/sql_databases/sql_app/crud.py!}
```

!!! tip
    By creating functions that are only dedicated to interacting with the database (get a user or an item) independent of your *path operation function*, you can more easily reuse them in multiple parts and also add <abbr title="Automated tests, written in code, that check if another piece of code is working correctly.">unit tests</abbr> for them.

### Create data

But then, even though you still don't have your burgers, your work with the cashier is "on pause" ⏸, because you have to wait 🕙 for your burgers to be ready.

# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

    Note over client,tasks: Can raise exception for dependency, handled after response is sent
    Note over client,operation: Can raise HTTPException and can change the response
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise
        dep -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        dep -->> dep: Raise other exception
    end

    except Exception as e:
        errors: List[Exception] = []
        errors.append(e)
        try:
            data = vars(obj)
        except Exception as e:
            errors.append(e)
            raise ValueError(errors) from e
    return jsonable_encoder(
        data,
        include=include,
        exclude=exclude,
        by_alias=by_alias,
        exclude_unset=exclude_unset,

## Detalles Técnicos

Las versiones modernas de Python tienen soporte para **"código asíncrono"** usando algo llamado **"coroutines"**, usando la sintaxis **`async` y `await`**.

Veamos esa frase por partes en las secciones siguientes:

* **Código Asíncrono**
* **`async` y `await`**
* **Coroutines**

## Código Asíncrono

    Note over client,tasks: Can raise exception for dependency, handled after response is sent
    Note over client,operation: Can raise HTTPException and can change the response
    client ->> dep: Start request
    Note over dep: Run code up to yield
    opt raise
        dep -->> handler: Raise HTTPException
        handler -->> client: HTTP error response
        dep -->> dep: Raise other exception
    end

    ```Python hl_lines="6  11"
    {!> ../../../docs_src/dependencies/tutorial006.py!}
    ```

### Вызов исключений

Зависимости из dependencies могут вызывать исключения с помощью `raise`, как и обычные зависимости:

=== "Python 3.9+"

    ```Python hl_lines="10  15"
    {!> ../../../docs_src/dependencies/tutorial006_an_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9  14"