code: def sortable_sortkey_title(instance):
      
      title = sortable_title(instance)
      if safe_callable(title):
          title = title()
  
      sort_key = instance.getSortKey()
      if sort_key is None:
          sort_key = 999999
  
      return "{:010.3f}{}".format(sort_key, title)
docs: Returns a sortable title as a mxin of sortkey + lowercase sortable_title