Does it possible to adapt the script "arrow key rotation 3D view" to a selection? :)

When nothing is selected the 3Dview is rotated with the arrow key
When something is selected the selection is rotated with the arrow key (useful in any view!)
/ by the center of gravity of the selection (or by an another point) ?

I suppose yes, but I am some rusted for this little brain sport ;)
Maybe enter somewhere a numeric angle rotation will be also useful
actually 6° can't make 10° :)