[yt-users] Shock Finding

Dear all, I am trying to figure out a way to mask out cells that contain shocks. One way I can think of is to create a derived field by identifying shocks. It seems that there are different ways of finding shocks: Enzo has a refinement criterion (refine by shocks) and there is also shock finding written by Sam. Has anybody tried to find shocks using yt? I would appreciate it if you would like to share your code/experience/advice. Thank you! Yuan