code: def finalize(self):
      super(PureNcclCommunicator, self).finalize()
      if self.nccl_comm is not None:
          chainer.cuda.Stream.null.synchronize()
          self.mpi_comm.barrier()
          self.nccl_comm.destroy()
          self.nccl_comm = None
  
file_path: chainer/chainermn/communicators/pure_nccl_communicator.py
imports: import warnings
  import chainer.cuda
  from chainermn.communicators import _communication_utility
  from chainermn.communicators import _memory_utility
  from chainermn.communicators import mpi_communicator_base
  from chainermn import nccl
  import numpy
label_desc: Use image node_id 2 for calling the PureNcclCommunicator obj's underlying member method code with example usage: obj.finalize() without return types