How to get detected known object position?

Question

I am using this code to detect learned objects: http://doc.aldebaran.com/2-4/dev/python/examples/vision/vision_recognition.html

The robot recognize a learned object if I show him one which is fine, Now, I want to make him move to that object if it is a bit far from here using the following:

# move to target and leave only 0.1 meters distance from torso
self.tracker.setRelativePosition([-0.1, 0.0, 0.0, 0.1, 0.1, 0.3])
self.tracker.setMode("Move")
target_position = self.tracker.getTargetPosition(0)
print("target position ",target_position)

But this simply does nothing. Is there another way to make the robot move to the recognized target?