Address code review feedback - fix type hints and simplify test logic

Co-authored-by: thinkall <3197038+thinkall@users.noreply.github.com>

Author: Copilot

flaml/automl/automl.py

@@ -749,7 +749,7 @@ def score(
 
     def predict(
         self,
-        X: np.array | DataFrame | list[str] | list[list[str]] | psDataFrame,
+        X: np.ndarray | DataFrame | list[str] | list[list[str]] | psDataFrame,
         **pred_kwargs,
     ):
         """Predict label from features.
@@ -817,7 +817,7 @@ def predict_proba(self, X, **pred_kwargs):
 
     def preprocess(
         self,
-        X: np.array | DataFrame | list[str] | list[list[str]] | psDataFrame,
+        X: np.ndarray | DataFrame | list[str] | list[list[str]] | psDataFrame,
     ):
         """Preprocess data using task-level preprocessing.
 

test/automl/test_preprocess_api.py

@@ -101,11 +101,10 @@ def test_automl_preprocess_with_dataframe(self):
         # Test preprocessing
         X_preprocessed = automl.preprocess(X_test)
 
-        # Verify the output
+        # Verify the output - check the number of rows matches
         self.assertIsNotNone(X_preprocessed)
-        # The preprocessed data should have the same number of rows
-        self.assertEqual(len(X_preprocessed) if hasattr(X_preprocessed, '__len__') else X_preprocessed.shape[0], 
-                         len(X_test))
+        preprocessed_len = len(X_preprocessed) if hasattr(X_preprocessed, '__len__') else X_preprocessed.shape[0]
+        self.assertEqual(preprocessed_len, len(X_test))
 
     def test_estimator_preprocess(self):
         """Test estimator-level preprocessing."""