how to open/close nextage grippers in simulation

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I am using rtmros_nextage in simulation and would like the robot to pick up objects. So far I cannot even open or close the grippers. Minimal example that does not do anything:

1. rtmlaunch nextage_ros_bridge nextage_ros_bridge_simulation.launch
2. roslaunch nextage_moveit_config moveit_planning_execution.launch
3. ipython -i `rospack find nextage_ros_bridge`/script/nextage.py

Now running robot._hands.gripper_l_open() or robot._hands.gripper_l_close() does not have any effect. What do I do wrong? Any help appreciated.

UPDATE: Thank you for your answer. So what I did is (as far as I can see) excatly what you describe in the tutorial. This is copy-pasted from my ipython:

In [1]: robot._hands.gripper_l_close()
dout, mask:
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2]
Out[1]: True

Not sure if the last line means the closing was successful, but I cannot see any movement of the gripper in the simulation and it should be visible shouldn't it?

rosversion nextage_ros_bridge
0.7.11
rospack find nextage_ros_bridge
/home/USERNAME/catkin_ws/src/rtmros_nextage/nextage_ros_bridge

And I am using ROS Indigo.

I also tried what the user you linked was trying - but executing robot._hands.handtool_l_eject()or robot._hands.handtool_l_attach() behaves the same way: output is True, but I cannot see anything happening in the simulation.