classes[it.simpleName] = c
        }
        [OldBase, OldSub, NewBase, NewSub].each {
            classes[it.simpleName] = instanceScopedPool.get(it.name)
        }

        classes['OldBase'].superclass = classes['OldSuperInternal']
        classes['NewBase'].superclass = classes['NewSuperInternal']
        classes['OldSub'].superclass = classes['OldBase']

WebSocketErrorModel: type[BaseModel] = create_model("WebSocket")


class FastAPIError(RuntimeError):
    """
    A generic, FastAPI-specific error.
    """


class DependencyScopeError(FastAPIError):
    """
    A dependency declared that it depends on another dependency with an invalid
    (narrower) scope.
    """


class ValidationException(Exception):
    def __init__(
        self,

## Installation

Create and activate a <a href="https://fastapi.tiangolo.com/virtual-environments/" class="external-link" target="_blank">virtual environment</a> and then install FastAPI:

<div class="termy">

```console
$ pip install "fastapi[standard]"

---> 100%
```

</div>

* <a href="https://strawberry.rocks/" class="external-link" target="_blank">Strawberry</a> 🍓
    * With <a href="https://strawberry.rocks/docs/integrations/fastapi" class="external-link" target="_blank">docs for FastAPI</a>
* <a href="https://ariadnegraphql.org/" class="external-link" target="_blank">Ariadne</a>
    * With <a href="https://ariadnegraphql.org/docs/fastapi-integration" class="external-link" target="_blank">docs for FastAPI</a>

### Eingabemodell in der Dokumentation { #input-model-in-docs }

Sie können überprüfen, dass das Feld `description` in der Dokumentation kein **rotes Sternchen** enthält, es ist nicht als erforderlich markiert:

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image01.png">
</div>

### Modell für die Ausgabe { #model-for-output }

Wenn Sie jedoch dasselbe Modell als Ausgabe verwenden, wie hier:

* <a href="https://strawberry.rocks/" class="external-link" target="_blank">Strawberry</a> 🍓
    * Con <a href="https://strawberry.rocks/docs/integrations/fastapi" class="external-link" target="_blank">documentación para FastAPI</a>
* <a href="https://ariadnegraphql.org/" class="external-link" target="_blank">Ariadne</a>

@pytest.fixture(name="client")
def get_client():
    from pydantic import BaseModel, ValidationInfo, field_validator

    app = FastAPI()

    class ModelB(BaseModel):
        username: str

    class ModelC(ModelB):
        password: str

    class ModelA(BaseModel):
        name: str
        description: Optional[str] = None
        foo: ModelB
        tags: dict[str, str] = {}

* <a href="https://strawberry.rocks/" class="external-link" target="_blank">Strawberry</a> 🍓
    * Com <a href="https://strawberry.rocks/docs/integrations/fastapi" class="external-link" target="_blank">docs para FastAPI</a>
* <a href="https://ariadnegraphql.org/" class="external-link" target="_blank">Ariadne</a>
    * Com <a href="https://ariadnegraphql.org/docs/fastapi-integration" class="external-link" target="_blank">docs para FastAPI</a>

* <a href="https://strawberry.rocks/" class="external-link" target="_blank">Strawberry</a> 🍓
    * Mit <a href="https://strawberry.rocks/docs/integrations/fastapi" class="external-link" target="_blank">Dokumentation für FastAPI</a>
* <a href="https://ariadnegraphql.org/" class="external-link" target="_blank">Ariadne</a>
    * Mit <a href="https://ariadnegraphql.org/docs/fastapi-integration" class="external-link" target="_blank">Dokumentation für FastAPI</a>

# =====================================================================================
# Without aliases


@app.get("/optional-str")
async def read_optional_str(p: Optional[str] = None):
    return {"p": p}


class QueryModelOptionalStr(BaseModel):
    p: Optional[str] = None


@app.get("/model-optional-str")
async def read_model_optional_str(p: Annotated[QueryModelOptionalStr, Query()]):
    return {"p": p.p}