code: def next_layout(pymux, variables):
      " Select next layout. "
      pane = pymux.arrangement.get_active_window()
      if pane:
          pane.select_next_layout(f next_layout(pymux, variables):
      " Select next layout. "
      pane = pymux.arrangement.get_active_window()
      if pane:
          pane.select_next_layout()
docs: Select next layout.