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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 ensure_permissions(mode_flags=stat.S_IWUSR):
 """decorator to ensure a filename has given permissions. If changed, original permissions are restored after the decorated modification. """


    def decorator(f):
        def modify(filename, *args, **kwargs):
            m = chmod_perms(filename) if exists(filename) else mode_flags
            if not m & mode_flags:
                os.chmod(filename, m | mode_flags)
            try:
                return f(filename, *args, **kwargs)
            finally:
                # restore original permissions
                if not m & mode_flags:
                    os.chmod(filename, m)
        return modify

    return decorator