code: def set_imu_callback(self, callback, data=None):
          
          self.imu_callback = callback
          self.imu_callback_data = data
docs: Register a callback for incoming IMU data packets.
          
          This method allows you to pass in a callbable which will be called on
          receipt of each IMU data packet sent by this SK8 device. Set to `None`
          to disable it again.
  
          Args:
              callback: a callable with the following signature:
                          (acc, gyro, mag, imu_index, seq, timestamp, data)
                        where:
                          acc, gyro, mag = sensor data ([x,y,z] in each case)
                          imu_index = originating IMU number (int, 0-4)
                          seq = packet sequence number (int, 0-255)
                          timestamp = value of time.time() when packet received
                          data = value of `data` parameter passed to this method
              data: an optional arbitrary object that will be passed as a 
                  parameter to the callback