docs: def add_context_menu_items(self, items, replace_items=False):
          '''Adds context menu items. If replace_items is True all
          previous context menu items will be removed.
          '''
          for label, action in items:
              assert isinstance(label, basestring)
              assert isinstance(action, basestring)
          if replace_items:
              self._context_menu_items = []
          self._context_menu_items.extend(items)
          self._listitem.addContextMenuItems(items, replace_items)