* {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> union(
      final Set<? extends E> set1, final Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override
      public int size() {
        int size = set1.size();

	for {
		select {
		case <-ctx.Done():
			return
		case <-timer.C:
			var wg sync.WaitGroup
			for _, set := range s.sets {
				wg.Add(1)
				go func(set *erasureObjects) {
					defer wg.Done()
					if set == nil {
						return
					}
					set.cleanupDeletedObjects(ctx)
				}(set)
			}
			wg.Wait()

			// Reset for the next interval
			timer.Reset(globalAPIConfig.getDeleteCleanupInterval())

    for (int i = 0; i < 0x1000; i++) {
      double setSize = rng.nextDouble();
      if (setSize < emptySetProportion) {
        sets[i] = ImmutableSet.of();
      } else if (setSize < emptySetProportion + singletonSetProportion) {
        sets[i] = ImmutableSet.of(PRESENT);
      } else {
        sets[i] = ImmutableSet.of(PRESENT, new Object());
      }

      if (rng.nextDouble() < hitRate) {
        queries[i] = PRESENT;

	}
	if len(formatV3.Erasure.Sets) != 1 {
		t.Fatalf("expected single set after migrating from v1 to v3, but found %d", len(formatV3.Erasure.Sets))
	}
	if !reflect.DeepEqual(formatV3.Erasure.Sets[0], m.Erasure.JBOD) {
		t.Fatalf("expected drive uuid: %v, got: %v", m.Erasure.JBOD, formatV3.Erasure.Sets[0])
	}

	m = &formatErasureV1{}
	m.Format = "unknown"

                  protected Set<String> create(String[] elements) {
                    Set<String> set = newHashSet(elements);
                    Set<String> other = newHashSet("wz", "xq");
                    set.addAll(other);
                    other.add("pq");
                    return Sets.difference(set, other);
                  }
                })
            .named("set - set")
            .withFeatures(

                  @Override
                  protected Set<String> create(String[] elements) {
                    Set<String> set1 = newHashSet(elements);
                    set1.add(samples().e3());
                    Set<String> set2 = newHashSet(elements);
                    set2.add(samples().e4());
                    return Sets.intersection(set1, set2);
                  }
                })

	tmpFormat.Erasure.This = ""
	if len(reference.Erasure.Sets) != len(format.Erasure.Sets) {
		return fmt.Errorf("Expected number of sets %d, got %d", len(reference.Erasure.Sets), len(format.Erasure.Sets))
	}

	// Make sure that the sets match.
	for i := range reference.Erasure.Sets {
		if len(reference.Erasure.Sets[i]) != len(format.Erasure.Sets[i]) {
			return fmt.Errorf("Each set should be of same size, expected %d got %d",

    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "b", "f"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("z"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("b", "d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("f", "d", "a"))));
  }

     *
     * @return The source of the POM or {@code null} if not set.
     */
    ModelSource getModelSource();

    /**
     * Sets the source of the POM to process. Eventually, either {@link #setModelSource(ModelSource)} or
     * {@link #setPomPath(Path)} must be set.
     *
     * @param modelSource The source of the POM to process, may be {@code null}.
     * @return This request, never {@code null}.
     */

- *If total drives has many common divisors the algorithm chooses the minimum amounts of erasure sets possible for a erasure set size of any N*.  In the example with 1024 drives - 4, 8, 16 are GCD factors. With 16 drives we get a total of 64 possible sets, with 8 drives we get a total of 128 possible sets, with 4 drives we get a total of 256 possible sets. So algorithm automatically chooses 64 sets, which is *16* 64 = 1024* drives in total.