code: def test_categorical_in_struct_nulls() -> None:
      s = pl.Series(
          "job",
          ["doctor", "waiter", None, None, None, "doctor"],
          pl.Categorical,
      )
      df = pl.DataFrame([s])
      s = (df.select(pl.col("job").value_counts(sort=True)))["job"]
  
      assert s[0] == {"job": None, "count": 3}
      assert s[1] == {"job": "doctor", "count": 2}
      assert s[2] == {"job": "waiter", "count": 1}
  
imports: from __future__ import annotations
  import contextlib
  import io
  import operator
  from typing import TYPE_CHECKING, Any, Callable, Literal
  import pytest
  import polars
  from polars import StringCache
  from polars.exceptions import CategoricalRemappingWarning, StringCacheMismatchError
  from polars.testing import assert_frame_equal, assert_series_equal
label_desc: Use image node_id 20 for calling a global function with example usage: test_categorical_in_struct_nulls() without return types