code: def test_catBoost_reference2(self):
      # The reference is from:
      #   https://www.youtube.com/watch?v=hqYQ8Yj9vB0
      # time:
      #     35:03
      # as obtained on 21 Aug 2019.
      # Note: they have an error at line [smooth 6 4.3 4.1]. It should be [smooth 6 4 4.1 3.9]
      X = pd.DataFrame(
          {
              "col1": [
                  "fuzzy",
                  "soft",
                  "smooth",
                  "fuzzy",
                  "smooth",
                  "soft",
                  "smooth",
                  "smooth",
              ]
          }
      )
      y = pd.Series([4, 1, 4, 3, 6, 0, 7, 5])
      enc = encoders.CatBoostEncoder()
      obtained = enc.fit_transform(X, y)
      prior = 30.0 / 8
      self.assertEqual(
          list(obtained["col1"]),
          [
              prior,
              prior,
              prior,
              (4 + prior) / 2,
              (4 + prior) / 2,
              (1 + prior) / 2,
              (10 + prior) / 3,
              (17 + prior) / 4,
          ],
      )
  
file_path: category_encoders/tests/test_cat_boost.py
imports: import pandas
  import numpy
  from unittest import TestCase
  import category_encoders
label_desc: Use image node_id 4 for calling the TestCatBoostEncoder obj's underlying member method code with example usage: obj.test_catBoost_reference2() without return types