code: def _init_comms(self):
      if self.nccl_comm is not None:
          return
      self.nccl_comm = _communication_utility.init_nccl_comm(
          self.mpi_comm
      )
  
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 3 for calling the PureNcclCommunicator obj's underlying member method code with example usage: obj._init_comms() without return types