def subscribe(self, topic, qos):
        """Subscribe to a topic."""
        assert isinstance(topic, str)

        if self.topics in topic:
            return
        result, mid = self._mqttc.subscribe(topic, qos)
        _raise_on_error(result)
        self.progress[mid] = topic
        self.topics[topic] = None
dataset/ETHPy150Open home-assistant/home-assistant/homeassistant/components/mqtt/__init__.py/MQTT.subscribe/swapped operands of `in`