code: public static <K, V> AbstractGroupExpression<Pair<K, V>, SortedMap<K, V>> sortedMap(Expression<K> key,
                                                                                          Expression<V> value,
                                                                                          Comparator<? super K> comparator) {
          return GMap.createSorted(QPair.create(key, value), comparator);
      }
docs: 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 comparator comparator for the created TreeMap instances
  @return wrapper expression