code: def _allocate_shared_memory(self):
      if self.measure_required():
          self.mem_bulk = None
      else:
          self.mem_bulk = sharedctypes.RawArray(
              "b", self.batch_size * self.mem_size
          )
  
imports: from __future__ import division
  import datetime
  import multiprocessing
  from multiprocessing import sharedctypes
  import signal
  import sys
  import threading
  import warnings
  import numpy
  import six
  from chainer.dataset import iterator
  from chainer.iterators import _statemachine
  from chainer.iterators.order_samplers import ShuffleOrderSampler
label_desc: Use image node_id 6 for calling the _PrefetchLoop obj's underlying member method code with example usage: obj._allocate_shared_memory() without return types