code: def test_write_read(self):
      writer = datasets.PickleDatasetWriter(self.io)
      writer.write(1)
      writer.write("hello")
      writer.write(1.5)
      writer.flush()
  
      dataset = datasets.PickleDataset(self.io)
      assert len(dataset) == 3
      assert dataset[0] == 1
      assert dataset[2] == 1.5
      assert dataset[1] == "hello"
  
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 2 for calling the TestPickleDataset obj's underlying member method code with example usage: obj.test_write_read() without return types