code: def test_multi_threads(self):
      num = 0
      with subprocess.Popen(
          f"python -m torch.backends.xeon.run_cpu --ninstances 4 --use-default-allocator \
              --disable-iomp --disable-numactl --disable-taskset --log-path {self._test_dir} --no-python pwd",
          shell=True,
          stdout=subprocess.PIPE,
          stderr=subprocess.STDOUT,
      ) as p:
          for line in p.stdout.readlines():
              segs = str(line, "utf-8").strip().split("-")
              if segs[-1].strip() == "pwd":
                  num += 1
      assert (
          num == 4
      ), "Failed to launch multiple instances for inference"
  
file_path: pytorch/test/backends/xeon/test_launch.py
imports: from torch.testing._internal.common_utils import TestCase, run_tests, IS_LINUX
  import shutil
  import subprocess
  import tempfile
  import unittest
label_desc: Use image node_id 4 for calling the TestTorchrun obj's underlying member method code with example usage: obj.test_multi_threads() without return types