code: def test_struct_group_by_field_agg_4216() -> None:
      df = pl.DataFrame([{"a": {"b": 1}, "c": 0}])
  
      result = df.group_by("c").agg(
          pl.col("a").struct.field("b").count()
      )
      expected = {"c": [0], "b": [1]}
      assert result.to_dict(as_series=False) == expected
  
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 29 for calling a global function with example usage: test_struct_group_by_field_agg_4216() without return types