Update art/estimators/classification/pytorch.py

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

Author: beat-buesser

art/estimators/classification/pytorch.py

@@ -505,7 +505,7 @@ def clone_for_refitting(self) -> "PyTorchClassifier":  # lgtm [py/inheritance/in
         model = copy.deepcopy(self.model)
 
         if self._optimizer is None:  # pragma: no cover
-            raise ValueError("An optimizer is needed to train the model, but none for provided.")
+            raise ValueError("An optimizer is needed to train the model, but none is provided.")
 
         # create a new optimizer that binds to the cloned model's parameters and uses original optimizer's defaults
         new_optimizer = type(self._optimizer)(model.parameters(), **self._optimizer.defaults)  # type: ignore