code: def test_truncation(self):
      tokenizer = CodeGenTokenizer.from_pretrained(
          "Salesforce/codegen-350M-mono"
      )
  
      text = "\nif len_a > len_b:\n    result = a\nelse:\n    result = b\n\n\n\n#"
      expected_trucated_text = (
          "\nif len_a > len_b:      result = a\nelse:      result = b"
      )
  
      input_ids = tokenizer.encode(text)
      truncation_pattern = [
          "^#",
          re.escape("<|endoftext|>"),
          "^'''",
          '^"""',
          "\n\n\n",
      ]
      decoded_text = tokenizer.decode(
          input_ids, truncate_before_pattern=truncation_pattern
      )
      self.assertEqual(decoded_text, expected_trucated_text)
  
imports: import json
  import os
  import re
  import unittest
  from transformers import CodeGenTokenizer, CodeGenTokenizerFast
  from transformers.models.codegen.tokenization_codegen import VOCAB_FILES_NAMES
  from transformers.testing_utils import require_tokenizers, slow
  from ...test_tokenization_common import TokenizerTesterMixin
label_desc: Use image node_id 11 for calling the CodeGenTokenizationTest obj's underlying member method code with example usage: obj.test_truncation() without return types