code: def test_where_categorical(frame_or_series):
      # https://github.com/pandas-dev/pandas/issues/18888
      exp = frame_or_series(
          pd.Categorical(
              ["A", "A", "B", "B", np.nan], categories=["A", "B", "C"]
          ),
          dtype="category",
      )
      df = frame_or_series(["A", "A", "B", "B", "C"], dtype="category")
      res = df.where(df != "C")
      tm.assert_equal(exp, res)
  
imports: import numpy
  import pytest
  from pandas._config import using_pyarrow_string_dtype
  from pandas.core.dtypes.common import is_integer
  import pandas
  from pandas import Series, Timestamp, date_range, isna
  import pandas._testing
label_desc: Use image node_id 19 for calling a global function with example usage: test_where_categorical(frame_or_series) without return types