code: def test_regex_cat(df_strings):
      """Test output on categorical columns"""
      df_strings.columns = df_strings.columns.astype("category")
      assert_frame_equal(
          df_strings.select_columns(re.compile(r"\d$")),
          df_strings.filter(regex=r"\d$"),
      )
  
imports: import datetime
  import re
  from itertools import product
  import numpy
  import pandas
  import pytest
  from pandas.api.types import is_numeric_dtype
  from pandas.testing import assert_frame_equal
  from janitor.functions.utils import DropLabel, get_columns, patterns
label_desc: Use image node_id 17 for calling a global function with example usage: test_regex_cat(df_strings) without return types