*
   * <p>The returned set and its constituent sets use {@code equals} to decide whether two elements
   * are identical, even if the input set uses a different concept of equivalence.
   *
   * <p><i>Performance notes:</i> while the power set of a set with size {@code n} is of size {@code
   * 2^n}, its memory usage is only {@code O(n)}. When the power set is constructed, the input set

 *   <li>Your value type's comparison method should be {@linkplain Comparable consistent with
 *       equals} if at all possible. Otherwise, be aware that concepts used throughout this
 *       documentation such as "equal", "same", "unique" and so on actually refer to whether {@link
 *       Comparable#compareTo compareTo} returns zero, not whether {@link Object#equals equals}