python怎么查看被改写后的方法？

如这句代码的endswith: fname.endswith('.gz')
在pycharm中按F3查看到的源码是：
def endswith(self, suffix, start=None, end=None): # real signature unknown; restored from __doc__
"""
S.endswith(suffix[, start[, end]]) -> bool

Return True if S ends with the specified suffix, False otherwise.
With optional start, test S beginning at that position.
With optional end, stop comparing S at that position.
suffix can also be a tuple of strings to try.
"""
return False
这个应该是父类的方法，怎么去看实质被调用的方法呢？

看 frame 是什么类咯，