@Override
  public Reiterator<Object> get(int tag) {
    return new SubIterator(tag);
  }
@Test
  public void testEmpties() {
    TaggedReiteratorList iter =
        create(
            new String[] {},
            new String[] {"a", "b", "c"},
            new String[] {},
            new String[] {},
            new String[] {"d"});
    assertEquals(iter.get(2) /*empty*/);
    assertEquals(iter.get(1), "a", "b", "c");
    assertEquals(iter.get(2) /*empty*/);
    assertEquals(iter.get(0) /*empty*/);
    assertEquals(iter.get(2) /*empty*/);
    assertEquals(iter.get(4), "d");
    assertEquals(iter.get(3) /*empty*/);
  }