//HOW can I use TestSetRegressionScoreFunction(RegressionValue val) for the scorefunction instead?
ScoreFunction<MultiLayerNetwork,DataSetIterator> scoreFunction = new TestSetAccuracyScoreFunction();

OptimizationConfiguration<DL4JConfiguration, MultiLayerNetwork, DataSetIterator, Object> configuration
            = new OptimizationConfiguration.Builder<DL4JConfiguration, MultiLayerNetwork, DataSetIterator, Object>()
                .candidateGenerator(candidateGenerator)
                .dataProvider(dataProvider)
                .modelSaver(modelSaver)
                .scoreFunction(scoreFunction)
                .terminationConditions(terminationConditions)
                .build();