@GwtIncompatible("NavigableSet")
  @Override
  public ImmutableSortedSet<E> subSet(
      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
    checkNotNull(fromElement);
    checkNotNull(toElement);
    checkArgument(comparator.compare(fromElement, toElement) <= 0);
    return subSetImpl(fromElement, fromInclusive, toElement, toInclusive);
  }
@ GwtIncompatible ( "NavigableSet" ) @ Override public ImmutableSortedSet < E > subSet ( E fromElement , boolean fromInclusive , E toElement , boolean toInclusive ) { checkNotNull ( fromElement ) ; checkNotNull ( toElement ) ; checkArgument ( comparator . compare ( fromElement , toElement ) <= 0 ) ; return subSetImpl ( fromElement , fromInclusive , toElement , toInclusive ) ; }
@since 12.0