code: def setUp(self):
      self.tmp_dir = tempfile.mkdtemp()
  
      for i in range(self.n_class):
          class_dir = os.path.join(self.tmp_dir, "{}".format(i))
          os.makedirs(class_dir)
          _save_img_file(
              os.path.join(class_dir, "img_0.png"), (48, 32), color=True
          )
  
imports: import numpy
  import os
  import shutil
  import tempfile
  import unittest
  from chainer import testing
  from chainercv.datasets import directory_parsing_label_names
  from chainercv.datasets import DirectoryParsingLabelDataset
  from chainercv.utils import assert_is_label_dataset
  from chainercv.utils import write_image
label_desc: Use image node_id 1 for calling the TestNumericalSortDirectoryParsingLabelDataset obj's underlying member method code with example usage: obj.setUp() without return types