'A L{MessageSet} contains a number if the number falls within
one of its ranges, and raises L{TypeError} if any range
contains L{None}.'

def test_contains(self):

    hasFive = MessageSet(1, 7)
    doesNotHaveFive = (MessageSet(1, 4) + MessageSet(6, 7))
    self.assertIn(5, hasFive)
    self.assertNotIn(5, doesNotHaveFive)
    hasFiveButHasNone = (hasFive + None)
    with self.assertRaises(TypeError):
        (5 in hasFiveButHasNone)
    hasFiveButHasNoneInSequence = (hasFive + (10, 12))
    hasFiveButHasNoneInSequence.add(8, None)
    with self.assertRaises(TypeError):
        (5 in hasFiveButHasNoneInSequence)
