def testPop(self): ks = KeyedSet(firstLetter, ["apple", "avocado", "banana"]) popped = [] while ks: popped.append(ks.pop()) self.assertEqual(sorted(popped), ["apple", "avocado", "banana"]) self.assertEqual(ks.subset_by_key("a"), set()) self.assertEqual(ks.subset_by_key("b"), set())