Method swapcase

Lib/test/test_bytes.py:2767–2770

(b, a)

            assert not c or c[-1] not in (0xdd, 0xcd)

        def swapcase(b, a):
            b.wait()
            c = a.swapcase()
            assert not c or c[-1] not in (0xdd, 0xcd)

        def title(b, a):
            b.wait()