Help for ocpp.sink.setup_sink_app

def setup_sink_app(*, app=None):
    """
    Basic OCPP passive sink for messages, acting as a dummy CSMS server.
    This won't pass compliance or provide authentication. It just accepts and logs all.
    Note: This version of the app was tested at the EVCS with real EVs.
    """
    # A - This line ensures we find just the kind of app we need or create one if missing
    if (_is_new_app := not (app := gw.unwrap_one((oapp := app), FastAPI))):
        app = FastAPI()

    @app.websocket("{path:path}")
    async def websocket_ocpp(websocket: WebSocket, path: str):
        gw.info(f"[OCPP] New WebSocket connection at /{path}")
        try:
            await websocket.accept()
            while True:
                raw = await websocket.receive_text()
                gw.info(f"[OCPP:{path}] Message received:", raw)

                try:
                    msg = json.loads(raw)
                    if isinstance(msg, list) and len(msg) >= 3 and msg[0] == 2:
                        message_id = msg[1]
                        action = msg[2]
                        payload = msg[3] if len(msg) > 3 else {}

                        gw.info(f"[OCPP:{path}] -> Action: {action} | Payload: {payload}")
                        response = [3, message_id, {"status": "Accepted"}]
                        await websocket.send_text(json.dumps(response))
                        gw.info(f"[OCPP:{path}] <- Acknowledged: {response}")
                    else:
                        gw.warning(f"[OCPP:{path}] Received non-Call message or malformed")
                except Exception as e:
                    gw.error(f"[OCPP:{path}] Error parsing message: {e}")
                    gw.debug(traceback.format_exc())

        except WebSocketDisconnect:
            gw.info(f"[OCPP:{path}] Disconnected")
        except Exception as e:
            gw.error(f"[OCPP:{path}] WebSocket error: {e}")
            gw.debug(traceback.format_exc())

    # B- This return pattern ensures we include our app in the bundle (if any)
    if _is_new_app:
        return app if not oapp else (oapp, app)    
    return oapp