code: def test_categorical_string_ops(self):
      a = pd.Series(["a", "a", "b"], dtype="category")
      da = dd.from_pandas(a, 2)
      result = da.str.upper()
      expected = a.str.upper()
      assert_eq(result, expected)
  
imports: from __future__ import annotations
  import contextlib
  import operator
  import warnings
  import numpy
  import pandas
  import pytest
  import dask
  import dask.dataframe
  from dask.dataframe import _compat
  from dask.dataframe._compat import PANDAS_GE_150, PANDAS_GE_200, PANDAS_GE_210, tm
  from dask.dataframe._pyarrow import to_pyarrow_string
  from dask.dataframe.core import _concat
  from dask.dataframe.utils import assert_eq, clear_known_categories, get_string_dtype, make_meta, pyarrow_strings_enabled
label_desc: Use image node_id 5 for calling the TestCategoricalAccessor obj's underlying member method code with example usage: obj.test_categorical_string_ops() without return types