public static <I> List<I> combineCollections(Collection<Collection<I>> collections) {
        return combineCollections(collections, Function.identity());
    }
Apply a specified transformation {@link Function} to every value in a Map.
@param map the Map to be transformed
@param transformation the transformation function
@return the transformed Map
@param <K> the key type
@param <I> the pre-transform value type
@param <O> the post-transform value type
connect/runtime/src/main/java/org/apache/kafka/connect/util/ConnectUtils.java