code: def accel_rename_current_tab(self, *args):
          
          page_num = self.get_notebook().get_current_page()
          page = self.get_notebook().get_nth_page(page_num)
          self.get_notebook().get_tab_label(page).on_rename(None)
          return True
docs: Callback to show the rename tab dialog. Called by the accel
          key.