The user changed selection

def on_selection_changed(self, sel):
        """The user changed selection"""
        m, self.editing_iter = sel.get_selected()

        if self.editing_iter:
            self.editing_model = m[self.editing_iter][0]
            self.show_curr_model_view(self.editing_model, False)
            
        else: self.view.remove_currency_view()
            
        return