docs: private static MultiMapConfig.ValueCollectionType findCollectionType(Collection collection) {
          if (collection instanceof Set) {
              return MultiMapConfig.ValueCollectionType.SET;
          } else if (collection instanceof List) {
              return MultiMapConfig.ValueCollectionType.LIST;
          }
          throw new IllegalArgumentException("[" + collection.getClass() + "] is not a known MultiMapConfig.ValueCollectionType!");
      }