Don't refit StandardScaler to test data

toolkit.py

@@ -183,8 +183,10 @@ class KerasROOTClassification:
                 self._scaler = StandardScaler()
                 logger.info("Fitting StandardScaler to training data")
                 self._scaler.fit(self.x_train)
-                logger.info("Fitting StandardScaler to test data")
-                self._scaler.fit(self.x_test)
+                # i think this would refit to test data (and overwrite the parameters)
+                # probably we either want to fit only training data or training and test data together
+                # logger.info("Fitting StandardScaler to test data")
+                # self._scaler.fit(self.x_test)
                 joblib.dump(self._scaler, filename)
         return self._scaler