code: def test_window_10417() -> None:
      df = pl.DataFrame({"a": [1], "b": [1.2], "c": [2.1]})
  
      assert df.lazy().with_columns(
          [
              pl.col("b") - pl.col("b").mean().over("a"),
              pl.col("c") - pl.col("c").mean().over("a"),
          ]
      ).collect().to_dict(as_series=False) == {
          "a": [1],
          "b": [0.0],
          "c": [0.0],
      }
  
imports: from __future__ import annotations
  import numpy
  import pytest
  import polars
  from polars.testing import assert_frame_equal, assert_series_equal
label_desc: Use image node_id 19 for calling a global function with example usage: test_window_10417() without return types