code: def test_future_ping_pong(self):
      node = lp_courier.CourierNode(Server)
      handle = node.create_handle()
  
      # Bind all addresses
      address_builder.bind_addresses([node])
  
      threading.Thread(target=node.run).start()
      client = handle.dereference()
      self.assertEqual(client.futures.ping().result(), "pong")
      self.assertEqual(client.futures().result(), "called")
      # Make sure Tensorflow is not imported.
      self.assertNotIn("tensorflow", sys.modules)
  
imports: import datetime
  import sys
  import threading
  import time
  from unittest import mock
  from absl.testing import absltest
  import courier
  from launchpad.launch.test_multi_threading import address_builder
  from launchpad.nodes.courier import node
label_desc: Use image node_id 2 for calling the CourierNodeTest obj's underlying member method code with example usage: obj.test_future_ping_pong() without return types