code: def _check_example(example, n_class):
      assert len(example) >= 2, (
          "Each example must have at least two elements:"
          "img and label."
      )
  
      img, label = example[:2]
  
      assert_is_image(img, color=True)
  
      assert isinstance(
          label, np.ndarray
      ), "label must be a numpy.ndarray."
      assert (
          label.dtype == np.int32
      ), "The type of label must be numpy.int32."
      assert (
          label.shape == img.shape[1:]
      ), "The shape of label must be (H, W)."
      assert (
          label.min() >= -1 and label.max() < n_class
      ), "The value of label must be in [-1, n_class - 1]."
  
imports: import numpy
  import six
  from chainercv.utils.testing.assertions.assert_is_image import assert_is_image
label_desc: Use image node_id 2 for calling a global function with example usage: _check_example(example, n_class) without return types