当我尝试myset在以下代码中重命名时，我看到了以下消息。
class NumberGenerator:
def __init__(self):
self.__myset__ = set()
def uncount(self, i):
self.__myset__.add(i)
Refactor failed. module 'rope.base.ast' has no attribute 'Str'
[<FrameSummary file refactor.py, line 294 in watch>, <FrameSummary file refactor.py, line 274 in _process_request>, <FrameSummary file refactor.py, line 206 in _rename>, ...
这么长，你想看我可以给你看。这段代码有错吗？不过，它有效。为什么重构不起作用？