Programatically edit on TreeView?

[Joao Victor <jvital gmail com>]

If i put an editable CellRendererText in a TreeView, i get the
funcionality of editing the text when double-clicking a node. Now, how
can i start the edit *without* double-clicking a node? For instance,
if i'd want to start editing after i click on a Button. How do i do
that?

Thanks,
J.V.