Expose feature and label transformer in automl.py (#993)

* expose label and feature transformer

* linter apply

* avoid undefined attribute in flaml/automl/automl.py

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

* avoid undefined attribute in flaml/automl/automl.py

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

* retrigger checks

* retrigger checks

---------

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

flaml/automl/automl.py

@@ -490,6 +490,16 @@ class AutoML(BaseEstimator):
         with open(filename, "w") as f:
             json.dump(best, f)
 
+    @property
+    def feature_transformer(self):
+        """Returns AutoML Transformer"""
+        return getattr(self, "_transformer", None)
+
+    @property
+    def label_transformer(self):
+        """Returns AutoML label transformer"""
+        return getattr(self, "_label_transformer", None)
+
     @property
     def classes_(self):
         """A numpy array of shape (n_classes,) for class labels."""