code: def testMessageToString(self):
      message = unittest_pb2.ForeignMessage()
      message.c = 123
      self.assertEqual("c: 123\n", str(message))
  
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 16 for calling the TextFormatTest obj's underlying member method code with example usage: obj.testMessageToString() without return types