code: def start_trajectory(self, trajectory_id, time_scale=1.0, relative=False,
                           reversed=False, group_mask=ALL_GROUPS):
          
          self._send_packet(struct.pack('<BBBBBf',
                                        self.COMMAND_START_TRAJECTORY,
                                        group_mask,
                                        relative,
                                        reversed,
                                        trajectory_id,
                                        time_scale))
docs: starts executing a specified trajectory
  
          :param trajectory_id: id of the trajectory (previously defined by
                 define_trajectory)
          :param time_scale: time factor; 1.0 = original speed;
                                          >1.0: slower;
                                          <1.0: faster
          :param relative: set to True, if trajectory should be shifted to
                 current setpoint
          :param reversed: set to True, if trajectory should be executed in
                 reverse
          :param group_mask: mask for which CFs this should apply to
          :return: