public static <K, V, T, U> AbstractGroupExpression<Pair<K, V>, SortedSetMultimap<T, U>> sortedSetMultimap(GroupExpression<K, T> key,
                                                                                                              GroupExpression<V, U> value,
                                                                                                              Comparator<? super T> keyComparator,
                                                                                                              Comparator<? super U> valueComparator) {
        return new GMultimap.Mixin<K, V, T, U, SortedSetMultimap<T, U>>(key, value, GMultimap.createSorted(QPair.create(key, value), keyComparator, valueComparator));
    }
Create a new aggregating map expression using a backing TreeMap using the given comparator

@param key key for the map entries
@param value value for the map entries
@param keyComparator comparator for the created TreeMap instances
@param valueComparator comparator for the created TreeMap instances
@return wrapper expression
querydsl-guava/src/main/java/com/querydsl/core/group/guava/GuavaGroupBy.java