Widget that shows a labeled border

I'm starting to use wxPython, and I'm trying to find which widget gives me a
labeled border around other widgets. Something like you can see in the font
selector options in this screenshot:
http://www.linuxsoft.cz/screenshot_img/843-a.jpg

I know I've already seen it in the demo, but I've already searched for it
twice and failed.

regards,
Paulo