code: def test_handle_unknown_value(self):
      train = pd.DataFrame({"city": ["chicago", "los angeles"]})
      test = pd.DataFrame({"city": ["chicago", "denver"]})
      y = pd.Series([1, 0])
  
      for encoder_name in set(encoders.__all__) - {
          "HashingEncoder"
      }:  # HashingEncoder supports new values by design -> excluded
          with self.subTest(encoder_name=encoder_name):
              enc = getattr(encoders, encoder_name)(
                  handle_unknown="value"
              )
              enc.fit(train, y)
              result = enc.transform(test)
              self.assertFalse(result.iloc[1, :].isna().all())
  
imports: import warnings
  from datetime import timedelta
  import numpy
  from numpy.testing import assert_array_equal
  import pandas
  import sklearn
  import tests.helpers
  from sklearn.utils.estimator_checks import check_transformer_general, check_transformers_unfitted, check_n_features_in
  from sklearn.compose import ColumnTransformer
  from unittest import TestCase
  from copy import deepcopy
  import category_encoders
label_desc: Use image node_id 12 for calling the TestEncoders obj's underlying member method code with example usage: obj.test_handle_unknown_value() without return types