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 create_worker(self, filename, outdir, target, **kwds):
      return multiprocessing.Process(
          target=self.save,
          args=(filename, outdir, target, self._savefun),
          kwargs=self._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 2 for calling the ProcessWriter obj's underlying member method code with example usage: obj.create_worker(filename, outdir, target) and returns: multiprocessing