Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(1, powerSet.size());
    assertEquals(ImmutableSet.of(ImmutableSet.of()), powerSet);
    assertEquals(0, powerSet.hashCode());
  }

  public void testPowerSetContents() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2, 3);
    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(8, powerSet.size());

    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(1, powerSet.size());
    assertEquals(ImmutableSet.of(ImmutableSet.of()), powerSet);
    assertEquals(0, powerSet.hashCode());
  }

  public void testPowerSetContents() {
    ImmutableSet<Integer> elements = ImmutableSet.of(1, 2, 3);
    Set<Set<Integer>> powerSet = powerSet(elements);
    assertEquals(8, powerSet.size());

        return inputSet.keySet().containsAll(set);
      }
      return false;
    }

    @Override
    public boolean equals(@CheckForNull Object obj) {
      if (obj instanceof PowerSet) {
        PowerSet<?> that = (PowerSet<?>) obj;
        return inputSet.keySet().equals(that.inputSet.keySet());
      }
      return super.equals(obj);
    }

    @Override
    public int hashCode() {
      /*

  /** The HTTP {@code X-Frame-Options} header field name. */
  public static final String X_FRAME_OPTIONS = "X-Frame-Options";
  /** The HTTP {@code X-Powered-By} header field name. */
  public static final String X_POWERED_BY = "X-Powered-By";
  /**
   * The HTTP <a href="http://tools.ietf.org/html/draft-evans-palmer-key-pinning">{@code
   * Public-Key-Pins}</a> header field name.
   *
   * @since 15.0
   */

deleting previously applied objects that have been removed from the input manifest. This feature has remained in alpha ever since due to performance and correctness issues inherent in its design. This PR exposes a second, independent pruning alpha powered by a new standard named `ApplySets`. An `ApplySet` is a server-side object (by default, a Secret; ConfigMaps are also allowed) that kubectl can use to accurately and efficiently track set membership across `apply` operations. The format used for `ApplySet`...