* use the {@code TreeSet} constructor directly, taking advantage of <a
   * href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
   *
   * @return a new, empty {@code TreeSet}
   */
  @SuppressWarnings("rawtypes") // https://github.com/google/guava/issues/989
  public static <E extends Comparable> TreeSet<E> newTreeSet() {
    return new TreeSet<>();
  }

  /**

   *
   * <p><b>Warning:</b> by definition, this comparator is not <i>consistent with equals</i> (as
   * defined {@linkplain Comparator here}). Avoid its use in APIs, such as {@link
   * TreeSet#TreeSet(Comparator)}, where such consistency is expected.
   *
   * <p>The returned comparator is serializable.
   *
   * <p><b>Java 8+ users:</b> Use the lambda expression {@code (a, b) -> 0} instead (in certain

   *
   * <p><b>Note:</b>If you only need to know whether two maps have the same mappings, call {@code
   * left.equals(right)} instead of this method.
   *
   * @param left the map to treat as the "left" map for purposes of comparison
   * @param right the map to treat as the "right" map for purposes of comparison
   * @return the difference between the two maps
   */
  public static <K extends @Nullable Object, V extends @Nullable Object>