code: def test_fit_transform_integers(self):
      # training data
      d = {
          "col1": [1, 2, 3],
          "col2": ["a", "a", "c"],
          "col3": [1, 1, 3],
          "col4": ["a", "b", "c"],
      }
      df = pd.DataFrame(data=d)
      categorical = PreprocessingCategorical(
          df.columns, PreprocessingCategorical.CONVERT_INTEGER
      )
      categorical.fit(df)
      df = categorical.transform(df)
      for col in ["col1", "col2", "col3", "col4"]:
          self.assertTrue(col in df.columns)
      self.assertEqual(df["col2"][0], 0)
      self.assertEqual(df["col2"][1], 0)
      self.assertEqual(df["col2"][2], 1)
      self.assertEqual(df["col4"][0], 0)
      self.assertEqual(df["col4"][1], 1)
      self.assertEqual(df["col4"][2], 2)
  
file_path: mljar-supervised/tests/tests_preprocessing/test_categorical_integers.py
imports: import unittest
  import tempfile
  import numpy
  import pandas
  from supervised.preprocessing.preprocessing_categorical import PreprocessingCategorical
label_desc: Use image node_id 3 for calling the CategoricalIntegersTest obj's underlying member method code with example usage: obj.test_fit_transform_integers() without return types