code: def testStartDispatcherWithPortConfig(self):
      port = pick_unused_port()
      config = server_lib.DispatcherConfig(port=port)
      dispatcher = server_lib.DispatchServer(config=config, start=True)
      self.assertEqual(
          dispatcher.target, "grpc://localhost:{}".format(port)
      )
  
imports: import logging
  import tempfile
  import threading
  import unittest
  from tensorflow.python.data.experimental.service import server_lib
  from tensorflow.python.framework import errors
  from tensorflow.python.platform import test
  from tensorflow.python.profiler import profiler_client
label_desc: Use image node_id 2 for calling the ServerLibTest obj's underlying member method code with example usage: obj.testStartDispatcherWithPortConfig() without return types