* that is not contained in {@code set1}.
   *
   * <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
   * equivalence relations, for example if {@code set1} is a {@link HashSet} and {@code set2} is a
   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> union(

    }

    protected void delete(final String entryDN, final Supplier<Hashtable<String, String>> envSupplier) {
        try (DirContextHolder holder = getDirContext(envSupplier)) {
            logger.debug("Deleting {}", entryDN);
            holder.get().destroySubcontext(entryDN);
        } catch (final NamingException e) {
            throw new LdapOperationException("Failed to delete " + entryDN, e);
        }
    }