code: def test_struct_arr_eval() -> None:
      df = pl.DataFrame(
          {
              "col_struct": [
                  [
                      {"a": 1, "b": 11},
                      {"a": 2, "b": 12},
                      {"a": 1, "b": 11},
                  ]
              ]
          }
      )
      assert df.with_columns(
          pl.col("col_struct")
          .list.eval(pl.element().first())
          .alias("first")
      ).to_dict(as_series=False) == {
          "col_struct": [
              [{"a": 1, "b": 11}, {"a": 2, "b": 12}, {"a": 1, "b": 11}]
          ],
          "first": [[{"a": 1, "b": 11}]],
      }
  
imports: from __future__ import annotations
  from dataclasses import dataclass
  from datetime import datetime, time
  from typing import TYPE_CHECKING
  import pandas
  import pyarrow
  import pytest
  import polars
  import polars.selectors
  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_struct_arr_eval() without return types