keep comment

Author: MarcoGorelli

pandas/core/frame.py

@@ -6161,6 +6161,7 @@ def f(vals) -> tuple[np.ndarray, int]:
         ):
             subset_iterable = (subset,)
         else:
+            #  needed for mypy since can't narrow types using np.iterable
             subset_iterable = cast(Iterable, subset)
 
         # Verify all columns in subset exist in the queried dataframe