code: def test_observation_aggregator_gpu_chainerx(
      use_chainer_variable, communicate_interval
  ):
      xp = chainerx
      communicator = chainermn.create_communicator("pure_nccl")
      device = get_device(communicator.intra_rank, True)
      with chainerx.using_device(device.device):
          if use_chainer_variable:
              run_test_observation_aggregator(
                  communicator,
                  xp,
                  use_chainer_variable,
                  communicate_interval,
                  use_gpu=True,
              )
          else:
              with pytest.raises(ValueError):
                  run_test_observation_aggregator(
                      communicator,
                      xp,
                      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 2 for calling a global function with example usage: test_observation_aggregator_gpu_chainerx(use_chainer_variable, communicate_interval) without return types