code: def test_reduce(self, dtype):
      self._run_test("reduce", dtype)
  
imports: import pathlib
  import subprocess
  import sys
  import unittest
  import os
  import numpy
  import pytest
  from cupy.cuda import nccl
  from cupy import testing
  from cupyx.distributed import init_process_group
  from cupyx.distributed._nccl_comm import _mpi_available
label_desc: Use image node_id 3 for calling the TestNCCLBackend obj's underlying member method code with example usage: obj.test_reduce(dtype) without return types