function unsubscribe(topic) {
  logger.info(`Unsubscribing to MQTT topic ${topic}`);
  if (this.mqttClient) {
    this.mqttClient.unsubscribe(topic);
  }
  delete this.topicBinds[topic];
}
@description Unsubscribes to a topic.
@param {string} topic - Topic to unsubscribe to.
@example
unsubscribe('topic/to/unsubscribe');