docs: def once(plugin, parent_stack=None):
      '''A run mode for the CLI that runs the plugin once and exits.'''
      plugin.clear_added_items()
      items = plugin.run()
  
      # if update_listing=True, we need to remove the last url from the parent
      # stack
      if parent_stack and plugin._update_listing:
          del parent_stack[-1]
  
      # if we have parent items, include the most recent in the display
      if parent_stack:
          items.insert(0, parent_stack[-1])
  
      display_listitems(items, plugin.request.url)
      return items