Is there a way to programatically attach assets together in the environment (e.g. attach a robot hand to the end of a robot arm)

I have two MJCF files, one for the robot arm and another for a robot hand. Is it possible to load both of them into IsaacGym and then attach the hand to the end of the arm through the Python interface? This makes it easier than having to modify the model files directly to attach the hand to the arm.