code: def test_group_by_multiple_column_reference() -> None:
      # Issue #7181
      df = pl.DataFrame(
          {
              "gr": ["a", "b", "a", "b", "a", "b"],
              "val": [1, 20, 100, 2000, 10000, 200000],
          }
      )
      res = df.group_by("gr").agg(
          pl.col("val") + pl.col("val").shift().fill_null(0),
      )
  
      assert res.sort("gr").to_dict(as_series=False) == {
          "gr": ["a", "b"],
          "val": [[1, 101, 10100], [20, 2020, 202000]],
      }
  
imports: from __future__ import annotations
  from collections import OrderedDict
  from datetime import datetime, timedelta
  from typing import Any
  import pytest
  import polars
  from polars.testing import assert_frame_equal, assert_series_equal
label_desc: Use image node_id 25 for calling a global function with example usage: test_group_by_multiple_column_reference() without return types