gtk2: frame with borders

[Nil Gradisnik <ghaefbgtk gmail com>]

I was told that "traditional frame style with borders, is deprecated".
Acording to: http://developer.gnome.org/projects/gup/hig/2.0/controls-frames.html

I use this frames in my Sysinfo: http://sysinfo.r8.org
I'm using gtkmm2 and have no idea how to make frames borderless. I
didn't found this frame option an gtkmm API documentation.

So is there an option for this ?
Thanks

_ghaefb