public Optional<String> serverAssignor() {
        return this.serverAssignor;
    }
@Test
    public void testMembershipManagerServerAssignor() {
        ConsumerMembershipManager membershipManager = createMembershipManagerJoiningGroup();
        assertEquals(Optional.empty(), membershipManager.serverAssignor());

        membershipManager = createMembershipManagerJoiningGroup("instance1", "Uniform");
        assertEquals(Optional.of("Uniform"), membershipManager.serverAssignor());
    }