code: def test_extend_self() -> None:
      df = pl.DataFrame({"a": [1, 2], "b": [True, False]})
  
      df.extend(df)
  
      expected = pl.DataFrame(
          {"a": [1, 2, 1, 2], "b": [True, False, True, False]}
      )
      assert_frame_equal(df, expected)
  
file_path: polars/py-polars/tests/unit/dataframe/test_extend.py
imports: from datetime import datetime
  import pytest
  import polars
  from polars.testing import assert_frame_equal
label_desc: Use image node_id 3 for calling a global function with example usage: test_extend_self() without return types