code: def testPrintNestedNewLineInStringAsOneLine(self):
      message = unittest_pb2.TestAllTypes()
      message.optional_string = "a\nnew\nline"
      self.CompareToGoldenText(
          text_format.MessageToString(message, as_one_line=True),
          'optional_string: "a\\nnew\\nline"',
      )
  
imports: import difflib
  import re
  import unittest
  from google.protobuf import text_format
  from google.protobuf.internal import test_util
  from google.protobuf import unittest_pb2
  from google.protobuf import unittest_mset_pb2
label_desc: Use image node_id 11 for calling the TextFormatTest obj's underlying member method code with example usage: obj.testPrintNestedNewLineInStringAsOneLine() without return types