docs: public static <T> Collection<T> emptyCollection(MultiMapConfig.ValueCollectionType collectionType) {
          switch (collectionType) {
              case SET:
                  return Collections.emptySet();
              case LIST:
                  return Collections.emptyList();
              default:
                  throw new IllegalArgumentException("[" + collectionType + "] is not a known MultiMapConfig.ValueCollectionType!");
          }
      }