class ResponseLevel0(JSONResponse):
    media_type = "application/x-level-0"


class ResponseLevel1(JSONResponse):
    media_type = "application/x-level-1"


class ResponseLevel2(JSONResponse):
    media_type = "application/x-level-2"


class ResponseLevel3(JSONResponse):
    media_type = "application/x-level-3"


class ResponseLevel4(JSONResponse):
    media_type = "application/x-level-4"

                "Error": {
                    "title": "Error",
                    "required": ["status", "title"],
                    "type": "object",
                    "properties": {
                        "status": {"title": "Status", "type": "string"},
                        "title": {"title": "Title", "type": "string"},
                    },
                },
                "JsonApiError": {

                "Error": {
                    "title": "Error",
                    "required": ["status", "title"],
                    "type": "object",
                    "properties": {
                        "status": {"title": "Status", "type": "string"},
                        "title": {"title": "Title", "type": "string"},
                    },
                },
                "JsonApiError": {
                    "title": "JsonApiError",

from fastapi.testclient import TestClient
from starlette.routing import Route

app = FastAPI()


class APIRouteA(APIRoute):
    x_type = "A"


class APIRouteB(APIRoute):
    x_type = "B"


class APIRouteC(APIRoute):
    x_type = "C"


router_a = APIRouter(route_class=APIRouteA)
router_b = APIRouter(route_class=APIRouteB)
router_c = APIRouter(route_class=APIRouteC)

                "Rectangle": {
                    "properties": {
                        "width": {"type": "integer", "title": "Width"},
                        "length": {"type": "integer", "title": "Length"},
                        "area": {"type": "integer", "title": "Area", "readOnly": True},
                    },
                    "type": "object",
                    "required": ["width", "length", "area"],

@needs_py310
def test_typing():
    types = {
        list[int]: [1, 2, 3],
        dict[str, list[int]]: {"a": [1, 2, 3], "b": [4, 5, 6]},
        set[int]: [1, 2, 3],  # `set` is converted to `list`
        tuple[int, ...]: [1, 2, 3],  # `tuple` is converted to `list`
    }
    for test_type, expect in types.items():
        app = FastAPI()

        @app.post("/", response_model=test_type)
        def post_endpoint(input: test_type):

```JSON
{"item_id":"foo"}
```

## Path parameters with types

You can declare the type of a path parameter in the function, using standard Python type annotations:

```Python hl_lines="7"
{!../../../docs_src/path_params/tutorial002.py!}
```

In this case, `item_id` is declared to be an `int`.

!!! check

7. Here the `response_model` is using a type annotation of a list of `Author` dataclasses.

    Again, you can combine `dataclasses` with standard type annotations.

8. Notice that this *path operation function* uses regular `def` instead of `async def`.

    As always, in FastAPI you can combine `def` and `async def` as needed.

                    "type": "object",
                    "properties": {"alias": {"title": "Alias", "type": "string"}},
                },
                "ModelNoAlias": {
                    "title": "ModelNoAlias",
                    "required": ["name"],
                    "type": "object",
                    "properties": {"name": {"title": "Name", "type": "string"}},

Hug was one of the first frameworks to implement the declaration of API parameter types using Python type hints. This was a great idea that inspired other tools to do the same.

It used custom types in its declarations instead of standard Python types, but it was still a huge step forward.

It also was one of the first frameworks to generate a custom schema declaring the whole API in JSON.