fixed bug in cv composer

cdplib/ml_validation/CVComposer.py

@@ -56,8 +56,8 @@ class CVComposer:
     def dummy_cv_and_concatenated_data_set(
             self,
             X_train: DataSetType,
-            y_train: Union[DataSetType, None] = None,
             X_test: DataSetType,
+            y_train: Union[DataSetType, None] = None,
             y_test: Union[DataSetType, None] = None)\
             -> Tuple[DataSetType, DataSetType, CVType]:
         """
@@ -205,4 +205,3 @@ class CVComposer:
             self._logger.log_and_raise_error(
                     ("Failed to make sliding window cv. "
                      "Exit with error: {}".format(e)))
-