def METHOD_NAME(self, backend):
    cipher = Cipher(
        algorithms.AES(binascii.unhexlify(b"0" * 32)),
        modes.CBC(binascii.unhexlify(b"0" * 32)),
        backend,
    )
    encryptor = cipher.encryptor()
    encryptor.update(b"a" * 16)
    encryptor.finalize()
    with pytest.raises(AlreadyFinalized):
        encryptor.update(b"b" * 16)
    with pytest.raises(AlreadyFinalized):
        encryptor.finalize()
    decryptor = cipher.decryptor()
    decryptor.update(b"a" * 16)
    decryptor.finalize()
    with pytest.raises(AlreadyFinalized):
        decryptor.update(b"b" * 16)
    with pytest.raises(AlreadyFinalized):
        decryptor.finalize()