code: def testMakeProtoPlaceholder_MapFieldScalarNoneValue(self):
      actual = resolve(
          _ExecutionInvocation(
              extra_flags={
                  "fookey": ph.exec_property(
                      "reload_policy"
                  ),  # Will be None.
                  "barkey": None,
                  "notnone": "this is not none",
              }
          ),
          exec_properties={},  # Intentionally empty.
      )
      self.assertProtoEquals(
          """
          extra_flags {
            key: "notnone"
            value: "this is not none"
          }
          """,
          parse_text_proto(actual),
      )
  
imports: import base64
  import functools
  from typing import Any, Dict, Optional, Type, TypeVar
  import tensorflow
  from tfx.dsl.compiler import placeholder_utils
  from tfx.dsl.placeholder import placeholder
  from tfx.dsl.placeholder import proto_placeholder
  from tfx.orchestration.portable import data_types
  from tfx.proto.orchestration import execution_invocation_pb2
  from tfx.proto.orchestration import pipeline_pb2
  from google.protobuf import message
  from google.protobuf import text_format
  from ml_metadata.proto import metadata_store_pb2
label_desc: Use image node_id 31 for calling the ProtoPlaceholderTest obj's underlying member method code with example usage: obj.testMakeProtoPlaceholder_MapFieldScalarNoneValue() without return types