code: def test_vstack_in_place(
      df1: pl.DataFrame, df2: pl.DataFrame
  ) -> None:
      df1.vstack(df2, in_place=True)
      expected = pl.DataFrame(
          {
              "foo": [1, 2, 3, 4],
              "bar": [6, 7, 8, 9],
              "ham": ["a", "b", "c", "d"],
          }
      )
      assert_frame_equal(df1, expected)
  
file_path: polars/py-polars/tests/unit/dataframe/test_vstack.py
imports: import pytest
  import polars
  from polars.testing import assert_frame_equal
label_desc: Use image node_id 4 for calling a global function with example usage: test_vstack_in_place(df1, df2) without return types