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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def chdir(method):
 """Decorator executing method in directory 'dir'. """

    def wrapper(self, dir, *args, **kw):
        dirstack = ChdirStack()
        dirstack.push(dir)
        try:
            return method(self, dir, *args, **kw)
        finally:
            dirstack.pop()

    return functools.wraps(method)(wrapper)