code: def testServeRunsWithoutExistingRuns(self):
      response = self.server.get(_ROUTE_PREFIX + "/runs")
      self.assertEqual(200, response.status_code)
      self.assertEqual(
          "application/json", response.headers.get("content-type")
      )
      self.assertEqual(json.loads(response.get_data()), dict())
  
imports: import collections
  import json
  import os
  import socket
  import threading
  import tensorflow
  from werkzeug import test
  from werkzeug import wrappers
  from tensorboard.backend import application
  from tensorboard.plugins import base_plugin
  from tensorboard.plugins.debugger_v2 import debug_data_multiplexer
  from tensorboard.plugins.debugger_v2 import debugger_v2_plugin
label_desc: Use image node_id 7 for calling the DebuggerV2PluginTest obj's underlying member method code with example usage: obj.testServeRunsWithoutExistingRuns() without return types