def testClear(self): ks = KeyedSet(firstLetter, ["apple", "avocado", "banana"]) self.assertFalse(not ks) self.assertEqual(len(ks), 3) ks.clear() self.assertEqual(len(ks), 0) self.assertTrue(not ks) self.assertEqual(ks.subset_by_key("a"), set()) self.assertEqual(ks.subset_by_key("b"), set())