test: add test for select after deduplicated join on DataFrame

- Verify that selecting columns works correctly after a join with deduplicate=True
- Confirm the joined DataFrame contains only matching IDs
- Test selecting single and multiple columns post-join to ensure correct data retrieval

Author: kosiew

python/tests/test_dataframe.py

@@ -2640,29 +2640,31 @@ def trigger_interrupt():
 def test_join_deduplicate_select():
     """Test that select works correctly after a deduplicated join."""
     ctx = SessionContext()
-    
+
     left_df = ctx.from_pydict({"id": [1, 2, 3], "name": ["Alice", "Bob", "Charlie"]})
-    right_df = ctx.from_pydict({"id": [2, 3, 4], "city": ["New York", "London", "Paris"]})
-    
+    right_df = ctx.from_pydict(
+        {"id": [2, 3, 4], "city": ["New York", "London", "Paris"]}
+    )
+
     # Join and select the id column to confirm it works
-    joined_df = left_df.join(right_df, on="id")
+    joined_df = left_df.join(right_df, on="id", deduplicate=True)
     selected_df = joined_df.select(column("id"))
     result = selected_df.collect()[0]
-    
+
     # Should have only the matching ids (2, 3)
     expected_ids = [2, 3]
     assert result.column(0).to_pylist() == expected_ids
-    
+
     # Also test selecting multiple columns
     multi_select_df = joined_df.select(column("id"), column("name"), column("city"))
     multi_result = multi_select_df.collect()[0]
-    
+
     expected_data = {
         "id": [2, 3],
-        "name": ["Bob", "Charlie"], 
-        "city": ["New York", "London"]
+        "name": ["Bob", "Charlie"],
+        "city": ["New York", "London"],
     }
-    
+
     assert multi_result.column(0).to_pylist() == expected_data["id"]
     assert multi_result.column(1).to_pylist() == expected_data["name"]
     assert multi_result.column(2).to_pylist() == expected_data["city"]