add TODOs

Author: mengxr

mllib/src/main/scala/org/apache/spark/ml/tuning/CrossValidator.scala

@@ -122,6 +122,7 @@ class CrossValidator extends Estimator[CrossValidatorModel] with CrossValidatorP
       trainingDataset.unpersist()
       var i = 0
       while (i < numModels) {
+        // TODO: duplicate evaluator to take extra params from input
         val metric = eval.evaluate(models(i).transform(validationDataset, epm(i)))
         logDebug(s"Got metric $metric for model trained with ${epm(i)}.")
         metrics(i) += metric

python/pyspark/ml/tuning.py

@@ -224,6 +224,7 @@ def fit(self, dataset, params={}):
             train = df.filter(~condition)
             for j in range(numModels):
                 model = est.fit(train, epm[j])
+                # TODO: duplicate evaluator to take extra params from input
                 metric = eva.evaluate(model.transform(validation, epm[j]))
                 metrics[j] += metric
         bestIndex = np.argmax(metrics)