code: def test_struct_null_count_strict_cast() -> None:
      s = pl.Series([{"a": None}]).cast(
          pl.Struct({"a": pl.Categorical})
      )
      assert s.dtype == pl.Struct([pl.Field("a", pl.Categorical)])
      assert s.to_list() == [{"a": None}]
  
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 45 for calling a global function with example usage: test_struct_null_count_strict_cast() without return types