def METHOD_NAME():
    in_labels = deepcopy(ref_in_labels)
    out_labels = combine_labels([in_labels, in_labels], [[], [2, 4, 6]],
                                ('group_in_m',), background_id=0,
                                merge_groups=False)
    exp_labels = deepcopy(ref_out_labels)
    exp_labels[exp_labels == 2] = 2 + 1e4
    exp_labels[exp_labels == 4] = 4 + 1e4
    exp_labels[exp_labels == 6] = 6 + 1e4
    assert_equal(out_labels, exp_labels)