Change self.preprocessing to self.preprocessing_operations

Signed-off-by: Beat Buesser <[email protected]>

Author: Beat Buesser

art/estimators/estimator.py

@@ -293,7 +293,7 @@ def _apply_preprocessing(self, x, y, fit: bool) -> Tuple[Any, Any]:
         :return: Tuple of `x` and `y` after applying the defences and standardisation.
         :rtype: Format as expected by the `model`
         """
-        if self.preprocessing:
+        if self.preprocessing_operations:
             for preprocess in self.preprocessing_operations:
                 if fit:
                     if preprocess.apply_fit: