docs: public static <T,K,V> Collection<T> collectMany(Map<K, V> self, Collection<T> collector, @ClosureParams(MapEntryOrKeyValue.class) Closure<Collection<? extends T>> projection) {
          for (Map.Entry<K, V> entry : self.entrySet()) {
              collector.addAll(callClosureForMapEntry(projection, entry));
          }
          return collector;
      }