code: def test_HandleUnknown_HaveUnknown_ExpectIndicatorInTest(self):
      train = ["A", "B", "C"]
      test = ["A", "B", "C", "D"]
  
      encoder = encoders.BaseNEncoder(handle_unknown="indicator")
      encoder.fit(train)
      result = encoder.transform(test)
  
      self.assertEqual(4, result.shape[0])
      self.assertListEqual([0, 0, 1], result.iloc[0, :].tolist())
      self.assertListEqual([0, 1, 0], result.iloc[1, :].tolist())
      self.assertListEqual([0, 1, 1], result.iloc[2, :].tolist())
      self.assertListEqual([1, 0, 0], result.iloc[3, :].tolist())
  
imports: import pandas
  from unittest import TestCase
  import numpy
  import category_encoders
label_desc: Use image node_id 6 for calling the TestBaseNEncoder obj's underlying member method code with example usage: obj.test_HandleUnknown_HaveUnknown_ExpectIndicatorInTest() without return types