code: def on_selection_changed(self, sel):
          
          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
docs: The user changed selection