code: def setUp(self):
      self.default_dataset_root = dataset.get_dataset_root()
      self.temp_dir = tempfile.mkdtemp()
      dataset.set_dataset_root(self.temp_dir)
  
imports: import os
  import shutil
  import tempfile
  import unittest
  import mock
  from chainer import dataset
  from chainer import testing
label_desc: Use image node_id 1 for calling the TestCacheOrLoadFile obj's underlying member method code with example usage: obj.setUp() without return types