code: def _start(self, *args, **kwargs):
      self._proc = mock.Mock()
      self._proc.stdin = None
      self._proc.stdout = None
      self._proc.stderr = None
      self._proc.pid = -1
  
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 1 for calling the TestSubprocessTransport obj's underlying member method code with example usage: obj._start() without return types