If it's greyed out it can't find the command, which probably means you've put the .py file in a subdirectory of your User (./Packages/User) folder, and not a direct
subdirectory of ./Packages. For some reason though, sublime-menu files are picked up from subdirectories of User. Weird I know.
So, you need the two files either
in a direct subdirectory of ./Packages, or
in the Packages/User folder, but not
in a subdirectory of Packages/User.
So on Linux, the directory will be directly under ~/.config/sublime-text-?/Packages
or you can dump the files into ~/.config/sublime-text-?/Packages/User (with no subdirectory)
where ? is 2 or 3
@MKANET, thanks for the thanks