Gtk::TreeStore with non-foldable children.

[Nathan Hüsken <gtkmm lonely-star org>]

Hello together,
I want to visualize objects which can be derived from each other in a 
TreeView. With "derived" I mean, that there are objects which are based 
on other objects. To show this relation, I was thinking of using the 
Gtk::TreeStore model, making derived objects children of the objects 
they are based on.
What I do not want is the list of children to be "foldable".
I mean, there should not be an arrow next to the parrent on which you 
can click and all children disappear.
Looking through the documentation, I found no function to provide this option.
Is it posible?
Thanks!
Nathan