code: def test_observation_aggregator_gpu_cupy(
      use_chainer_variable, communicate_interval
  ):
      communicator = chainermn.create_communicator("pure_nccl")
  
      run_test_observation_aggregator(
          communicator,
          cuda.cupy,
          use_chainer_variable,
          communicate_interval,
          use_gpu=True,
      )
  
file_path: chainer/tests/chainermn_tests/extensions_tests/test_observation_aggregator.py
imports: from __future__ import division
  import pytest
  import numpy
  import chainer
  import chainer.testing
  from chainer.training import extension
  from chainer.backend import cuda
  import chainermn
  from chainermn.testing import get_device
  from chainermn.extensions import ObservationAggregator
  import chainerx
label_desc: Use image node_id 3 for calling a global function with example usage: test_observation_aggregator_gpu_cupy(use_chainer_variable, communicate_interval) without return types