code: 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!");
      }
docs: Returns corresponding {@link MultiMapConfig.ValueCollectionType} of a {@link java.util.Collection}
  
  @param collection {@link MultiMapConfig.ValueCollectionType} to be find
  @return corresponding {@link MultiMapConfig.ValueCollectionType} of a {@link java.util.Collection}
  @throws java.lang.IllegalArgumentException if collectionType is unknown