code: def check_link_copyable(comm):
      #  Regression test for #5854
      bn0 = ModelDistributedBN(comm)
      bn1 = bn0.copy(mode="copy")
      assert bn1 is not None
      bn2 = MultiNodeBatchNormalization(10, comm)
      bn3 = bn2.copy(mode="copy")
      assert bn3 is not None
  
imports: import chainer
  from chainer.backends.cuda import cupy
  import chainer.testing
  import chainer.utils
  import mpi4py.MPI
  import numpy
  import pytest
  from chainermn.communicators.naive_communicator import NaiveCommunicator
  from chainermn.communicators.pure_nccl_communicator import PureNcclCommunicator
  from chainermn.links import MultiNodeBatchNormalization
  from chainermn import nccl
label_desc: Use image node_id 2 for calling a global function with example usage: check_link_copyable(comm) without return types