code: def test_preprocessing(self):
      preprocessor = Preprocessor()
      data = (
          ("First text!", "first head"),
          ("2-nd täxt", "Second head"),
      )
      data_preprocessed = [preprocessor(d) for d in data]
      self.assertEqual(
          ("<start> first text ! <end>", "<start> first head <end>"),
          data_preprocessed[0],
      )
      self.assertEqual(
          ("<start> #-nd täxt <end>", "<start> second head <end>"),
          data_preprocessed[1],
      )
  
      preprocessor = Preprocessor(
          start_token="<start>",
          end_token="<end>",
          lower_case=True,
          hash_numbers=False,
      )
      data_preprocessed = [preprocessor(d) for d in data]
      self.assertEqual(
          ("<start> 2-nd täxt <end>", "<start> second head <end>"),
          data_preprocessed[1],
      )
  
      preprocessor = Preprocessor(
          start_token="<start>",
          end_token="<end>",
          lower_case=False,
          hash_numbers=True,
      )
      data_preprocessed = [preprocessor(d) for d in data]
      self.assertEqual(
          ("<start> #-nd täxt <end>", "<start> Second head <end>"),
          data_preprocessed[1],
      )
  
imports: import unittest
  from headliner.preprocessing.preprocessor import Preprocessor
label_desc: Use image node_id 1 for calling the TestPreprocessor obj's underlying member method code with example usage: obj.test_preprocessing() without return types