* of each element is the <i>maximum</i> of its counts in the two backing multisets. The iteration
   * order of the returned multiset matches that of the element set of {@code multiset1} followed by
   * the members of the element set of {@code multiset2} that are not contained in {@code
   * multiset1}, with repeated occurrences of the same element appearing consecutively.

 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0 (implements {@code NavigableSet} since 12.0)
 */
// TODO(benyu): benchmark and optimize all creation paths, which are a mess now
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault

        if (!throwIfDuplicateKeys) {
          // We want to retain only the last-put value for any given key, before sorting.
          // This could be improved, but orderEntriesByValue is rather rarely used anyway.
          localAlternatingKeysAndValues = lastEntryForEachKey(localAlternatingKeysAndValues, size);
          if (localAlternatingKeysAndValues.length < alternatingKeysAndValues.length) {

  }

  /**
   * Creates an empty {@code Set} that uses identity to determine equality. It compares object
   * references, instead of calling {@code equals}, to determine whether a provided object matches
   * an element in the set. For example, {@code contains} returns {@code false} when passed an
   * object that equals a set member, but isn't the same instance. This behavior is similar to the