[Inkscape-devel] Needing to make a layer or graphics non printable

Hi, I am needing the ability to make a layer non printable. Can some one point me to the right area in the code to possibly activate this feature? I did some searching and found the attribute sodipodi:nonprintable here http://inkscape.modevia.com/doxygen/html/attributes_8cpp-source.php on line 00037 but it does not seem to work on a layer or graphic when I use that attribute in the xml editor. How can I activate this attribute?