code: def define_trajectory(self, trajectory_id, offset, n_pieces):
          
          self._send_packet(struct.pack('<BBBBIB',
                                        self.COMMAND_DEFINE_TRAJECTORY,
                                        trajectory_id,
                                        self.TRAJECTORY_LOCATION_MEM,
                                        self.TRAJECTORY_TYPE_POLY4D,
                                        offset,
                                        n_pieces))
docs: Define a trajectory that has previously been uploaded to memory.
  
          :param trajectory_id: The id of the trajectory
          :param offset: offset in uploaded memory
          :param n_pieces: Nr of pieces in the trajectory
          :return: