code: def test_group_by_custom_agg_empty_list() -> None:
      assert (
          pl.DataFrame(
              [
                  pl.Series("key", [], dtype=pl.Categorical),
                  pl.Series("val", [], dtype=pl.Float64),
              ]
          )
          .group_by("key")
          .agg(
              [
                  pl.col("val").mean().alias("mean"),
                  pl.col("val").std().alias("std"),
                  pl.col("val").skew().alias("skew"),
                  pl.col("val").kurtosis().alias("kurt"),
              ]
          )
      ).dtypes == [
          pl.Categorical,
          pl.Float64,
          pl.Float64,
          pl.Float64,
          pl.Float64,
      ]
  
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 11 for calling a global function with example usage: test_group_by_custom_agg_empty_list() without return types