Dear PyMol users!

I want to set transparency on the selected carton region of my protein ( I have closed GFP barell with the chromophore inside it so I'd like set transparency of some beta-shits to make chromophore easily visible ).

In PyMol I've selected region corresponded to that Beta-sheets and than used
set cartoon_transparency, 0.5, sele  

unfortunatelly there were no any changes after this :(

How I could solve it ?

Thanks for help,