Fixed copy() to copy models instead of list

Author: Louiszr

python/pyspark/ml/tests/test_tuning.py

@@ -125,9 +125,9 @@ def test_copy(self):
             'foo',
             "Changing the original avgMetrics should not affect the copied model"
         )
-        cvModel.subModels[0] = 'foo'
+        cvModel.subModels[0][0].getInducedError = lambda: 'foo'
         self.assertNotEqual(
-            cvModelCopied.subModels[0],
+            cvModelCopied.subModels[0][0].getInducedError(),
             'foo',
             "Changing the original subModels should not affect the copied model"
         )
@@ -777,9 +777,9 @@ def test_copy(self):
             'foo',
             "Changing the original validationMetrics should not affect the copied model"
         )
-        tvsModel.subModels[0] = 'foo'
+        tvsModel.subModels[0].getInducedError = lambda: 'foo'
         self.assertNotEqual(
-            tvsModelCopied.subModels[0],
+            tvsModelCopied.subModels[0].getInducedError(),
             'foo',
             "Changing the original subModels should not affect the copied model"
         )

python/pyspark/ml/tuning.py

@@ -480,7 +480,10 @@ def copy(self, extra=None):
             extra = dict()
         bestModel = self.bestModel.copy(extra)
         avgMetrics = list(self.avgMetrics)
-        subModels = [model.copy() for model in self.subModels]
+        subModels = [
+            [sub_model.copy() for sub_model in fold_sub_models]
+            for fold_sub_models in self.subModels
+        ]
         return self._copyValues(CrossValidatorModel(bestModel, avgMetrics, subModels), extra=extra)
 
     @since("2.3.0")