class_docstr: Snapshot writer that uses a separate process.
  
  This class creates a new process that invokes the actual saving function.
  
  .. note::
      Forking a new process from a MPI process might be danger. Consider
      using :class:`ThreadWriter` instead of ``ProcessWriter`` if you are
      using MPI.
  
  .. seealso::
  
      - :meth:`chainer.training.extensions.snapshot`
code: def __init__(self, savefun=npz.save_npz, **kwds):
      super(ProcessWriter, self).__init__(savefun=savefun, **kwds)
  
imports: import multiprocessing
  import os
  import shutil
  import threading
  from six.moves import queue
  from chainer.serializers import npz
  from chainer import utils
label_desc: Use image node_id 1 to create a new ProcessWriter object from inherited base classes: StandardWriter with example: obj = ProcessWriter(savefun)