*/
@SuppressWarnings("serial") // uses writeReplace, not default serialization
@GwtIncompatible
final class RegularImmutableSortedMultiset<E> extends ImmutableSortedMultiset<E> {
  private static final long[] zeroCumulativeCounts = {0};

  static final ImmutableSortedMultiset<?> NATURAL_EMPTY_MULTISET =
      new RegularImmutableSortedMultiset<>(Ordering.natural());

  @VisibleForTesting final transient RegularImmutableSortedSet<E> elementSet;