def test_setLastSingleWildcard(self):
        """
        Setting L{MessageSet.last} replaces L{None}, representing
        C{*}, with that number, making that L{MessageSet} iterable.
        """
        singleMessageReplaced = MessageSet(None)
        singleMessageReplaced.last = 10
        self.assertEqual(list(singleMessageReplaced), [10])

        rangeReplaced = MessageSet(3, None)
        rangeReplaced.last = 1
        self.assertEqual(list(rangeReplaced), [1, 2, 3])

        Setting L{MessageSet.last} replaces L{None}, representing
        C{*}, with that number, making that L{MessageSet} iterable.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py