Is the render_sub() function of Rsvg also capable of separating groups ?

Question

I am trying to separate Groups from an Svg-File.

Separating single elements such as rectangles is possible via Rsvgs. render_sub(cairo_context,"#rect1234") works well for me. Is there a way to also separate whole groups of elements you created in inkscape before? Like render_sub(cairo_context,"#g4321") [which doesn't work].