code: def test_get_gray(self):
      img, label = self.dataset.get_example(1)
      self.assertEqual(img.dtype, self.dtype)
      self.assertEqual(img.shape, (1, 300, 300))
  
      self.assertEqual(label.dtype, self.label_dtype)
      self.assertEqual(label, 1)
  
imports: import os
  import pickle
  import unittest
  import numpy
  from chainer import datasets
  from chainer.datasets import image_dataset
  from chainer import testing
label_desc: Use image node_id 4 for calling the TestLabeledZippedImageDataset obj's underlying member method code with example usage: obj.test_get_gray() without return types