in src/backend/app.py [0:0]
def on_stream_event(self, event: model.IoTCoreMessage) -> None:
"""
Invoked when a SubscriptionResponseMessage is received.
"""
payload = {"payload": json.loads(event.message.payload.decode())}
self.socket_io.emit("message", payload)
logger.info("message sent from SubscribeTopicHandler!")