code: def testMergeEmptyGroup(self):
      message = unittest_pb2.TestAllTypes()
      text = "OptionalGroup: {}"
      text_format.Merge(text, message)
      self.assertTrue(message.HasField("optionalgroup"))
  
      message.Clear()
  
      message = unittest_pb2.TestAllTypes()
      text = "OptionalGroup: <>"
      text_format.Merge(text, message)
      self.assertTrue(message.HasField("optionalgroup"))
  
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 30 for calling the TextFormatTest obj's underlying member method code with example usage: obj.testMergeEmptyGroup() without return types