Use explicit identity functions instead of lambda for better type safety

Copilot · franciscojavierarceo · Copilot · commit a735bfbd541d · 2026-01-23T06:48:04.000Z
Co-authored-by: franciscojavierarceo &lt;4163062+franciscojavierarceo@users.noreply.github.com&gt;
diff --git a/sdk/python/feast/transformation/pandas_transformation.py b/sdk/python/feast/transformation/pandas_transformation.py
@@ -152,8 +152,12 @@ def from_proto(
     ):
         if skip_udf:
             # Return a dummy transformation when skipping UDF deserialization
+            # Identity function that preserves DataFrame structure
+            def identity_udf(df: pd.DataFrame) -> pd.DataFrame:
+                return df
+
             return PandasTransformation(
-                udf=lambda x: x,  # Identity function as placeholder
+                udf=identity_udf,
                 udf_string=user_defined_function_proto.body_text,
             )
         return PandasTransformation(
diff --git a/sdk/python/feast/transformation/python_transformation.py b/sdk/python/feast/transformation/python_transformation.py
@@ -170,8 +170,12 @@ def from_proto(
     ):
         if skip_udf:
             # Return a dummy transformation when skipping UDF deserialization
+            # Identity function that preserves dictionary structure
+            def identity_udf(features_dict: Dict[str, Any]) -> Dict[str, Any]:
+                return features_dict
+
             return PythonTransformation(
-                udf=lambda x: x,  # Identity function as placeholder
+                udf=identity_udf,
                 udf_string=user_defined_function_proto.body_text,
             )
         return PythonTransformation(
