docs: public static <G, K, V> Map<G, List<Map.Entry<K, V>>> groupEntriesBy(Map<K, V> self, @ClosureParams(MapEntryOrKeyValue.class) Closure<G> closure) {
          final Map<G, List<Map.Entry<K, V>>> answer = new LinkedHashMap<G, List<Map.Entry<K, V>>>();
          for (Map.Entry<K, V> entry : self.entrySet()) {
              G value = callClosureForMapEntry(closure, entry);
              groupAnswer(answer, entry, value);
          }
          return answer;
      }