code: def flush_parent_cache(node):
      
      if node._parent is None:
          node._del_cache()
          return
      node._del_cache()
      flush_parent_cache(node._parent)
docs: Flush parent cache will recurse back up the tree and
      wipe the cache from each parent node reference on the
      given element. This allows the objects to be reused
      and a clean way to force the object to update itself
      if attributes or methods are referenced after update.