class_docstr: Writer class that makes PickleDataset.
  
  To make :class:`PickleDataset`, a user needs to prepare data using
  :class:`PickleDatasetWriter`.
  
  Args:
      writer: File like object that supports ``write`` and ``tell`` methods.
      protocol (int): Valid protocol for :mod:`pickle`.
  
  .. seealso: chainer.datasets.PickleDataset
code: def flush(self):
      if hasattr(self._writer, "flush"):
          self._writer.flush()
  
imports: import io
  import multiprocessing.util
  import threading
  import six
  import six.moves.cPickle
  from chainer.dataset import dataset_mixin
label_desc: Use image node_id 6 for calling the PickleDatasetWriter obj's underlying member method code with example usage: obj.flush() without return types