code: def test_subprocess_repr(self):
      waiter = self.loop.create_future()
      transport, protocol = self.create_transport(waiter)
      transport._process_exited(6)
      self.loop.run_until_complete(waiter)
  
      self.assertEqual(
          repr(transport),
          "<TestSubprocessTransport pid=-1 returncode=6>",
      )
      transport._returncode = None
      self.assertEqual(
          repr(transport), "<TestSubprocessTransport pid=-1 running>"
      )
      transport._pid = None
      transport._returncode = None
      self.assertEqual(
          repr(transport), "<TestSubprocessTransport not started>"
      )
      transport.close()
  
imports: import os
  import signal
  import sys
  import textwrap
  import unittest
  import warnings
  from unittest import mock
  import asyncio
  from asyncio import base_subprocess
  from asyncio import subprocess
  from test.test_asyncio import utils
  from test import support
  from test.support import os_helper
label_desc: Use image node_id 4 for calling the SubprocessTransportTests obj's underlying member method code with example usage: obj.test_subprocess_repr() without return types