def METHOD_NAME(self):
    # objects such as deques, sets, and dictionaries enforce
    # length immutability  during iteration
    it = self.it
    self.assertEqual(length_hint(it), n)
    next(it)
    self.assertEqual(length_hint(it), n-1)
    self.mutate()
    self.assertRaises(RuntimeError, next, it)
    self.assertEqual(length_hint(it), 0)