code: def test_get_categorical_cols(self):
      df = pd.DataFrame({"col": ["a", "b"]})
      self.assertEqual(
          get_categorical_cols(df.astype("object")), ["col"]
      )
      self.assertEqual(
          get_categorical_cols(df.astype("category")), ["col"]
      )
      self.assertEqual(
          get_categorical_cols(df.astype("string")), ["col"]
      )
  
file_path: category_encoders/tests/test_utils.py
imports: from unittest import TestCase
  from category_encoders.utils import convert_input_vector, convert_inputs, get_categorical_cols
  import pandas
  import numpy
label_desc: Use image node_id 3 for calling the TestUtils obj's underlying member method code with example usage: obj.test_get_categorical_cols() without return types