code: def start(self):
          
          # initialize subscribers
          self._image_sub = rospy.Subscriber(self.topic_image_color, sensor_msgs.msg.Image, self._color_image_callback)
          self._depth_sub = rospy.Subscriber(self.topic_image_depth, sensor_msgs.msg.Image, self._depth_image_callback)
          self._camera_info_sub = rospy.Subscriber(self.topic_info_camera, sensor_msgs.msg.CameraInfo, self._camera_info_callback)
          
          timeout = 10
          try:
              rospy.loginfo("waiting to recieve a message from the Kinect")
              rospy.wait_for_message(self.topic_image_color, sensor_msgs.msg.Image, timeout=timeout)
              rospy.wait_for_message(self.topic_image_depth, sensor_msgs.msg.Image, timeout=timeout)
              rospy.wait_for_message(self.topic_info_camera, sensor_msgs.msg.CameraInfo, timeout=timeout)
          except rospy.ROSException as e:
              print("KINECT NOT FOUND")
              rospy.logerr("Kinect topic not found, Kinect not started")
              rospy.logerr(e)
  
          while self._camera_intr is None:
              time.sleep(0.1)
          
          self._running = True
docs: Start the sensor