multiset.add(containsMultiset);
    ContainsBothWithMultisetFirst multisetFirst =
        new ContainsBothWithMultisetFirst(multiset, containsMultiset);
    ContainsBothWithContainsMultisetFirst containsMultisetFirst =
        new ContainsBothWithContainsMultisetFirst(containsMultiset, multiset);

    ContainsBothWithMultisetFirst reMultisetFirst = reserialize(multisetFirst);
    assertThat(reMultisetFirst.a.isEmpty()).isFalse();