code: def testExecutionDigestWithNoOutputToJson(self):
      execution_digest = debug_events_reader.ExecutionDigest(
          1234, 5678, "FooOp", output_tensor_device_ids=None
      )
      json = execution_digest.to_json()
      self.jsonRoundTripCheck(json)
      self.assertEqual(json["wall_time"], 1234)
      self.assertEqual(json["op_type"], "FooOp")
      self.assertEqual(json["output_tensor_device_ids"], None)
  
imports: import glob
  import json
  import os
  import re
  import threading
  import time
  from absl.testing import parameterized
  from tensorflow.core.protobuf import debug_event_pb2
  from tensorflow.python.debug.lib import debug_events_reader
  from tensorflow.python.debug.lib import debug_events_writer
  from tensorflow.python.debug.lib import dumping_callback_test_lib
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import test_util
  from tensorflow.python.framework import versions
  from tensorflow.python.platform import googletest
label_desc: Use image node_id 2 for calling the DataObjectsTest obj's underlying member method code with example usage: obj.testExecutionDigestWithNoOutputToJson() without return types