code: def init_nccl_comm(mpi_comm):
      from chainermn import nccl
  
      if mpi_comm.rank == 0:
          nccl_comm_id = nccl.get_unique_id()
      else:
          nccl_comm_id = None
      nccl_comm_id = mpi_comm.bcast(nccl_comm_id)
      return nccl.NcclCommunicator(
          mpi_comm.size, nccl_comm_id, mpi_comm.rank
      )
  
file_path: chainer/chainermn/communicators/_communication_utility.py
imports: from chainermn import nccl
  import collections
  import numpy
  import pickle
  import mpi4py.MPI
label_desc: Use image node_id 4 for calling a global function with example usage: init_nccl_comm(mpi_comm) and returns: nccl