code: def test_file_reader_picklable(self):
      m = mock.mock_open()
      with mock.patch("chainer.datasets.pickle_dataset.open", m):
          r = pickle_dataset._FileReader(self.path)
  
          m.assert_called_once_with(self.path, "rb")
  
          m.reset_mock()
          pickle.loads(pickle.dumps(r))
  
          m.assert_called_once_with(self.path, "rb")
  
imports: import ctypes
  import io
  import multiprocessing
  import os
  import pickle
  import platform
  import sys
  import unittest
  import mock
  from chainer import datasets
  from chainer.datasets import pickle_dataset
  from chainer import testing
  from chainer import utils
label_desc: Use image node_id 5 for calling the TestPickleDatasetHelper obj's underlying member method code with example usage: obj.test_file_reader_picklable() without return types