code: def test_read_image_as_grayscale(self):
      if self.backend == "cv2" and not _cv2_available:
          return
  
      with chainer.using_config("cv_read_image_backend", self.backend):
          img = read_image(
              self.file, dtype=self.dtype, color=False, alpha=self.alpha
          )
  
      self.assertEqual(img.shape, (1,) + self.size)
      self.assertEqual(img.dtype, self.dtype)
  
      if (
          self.format in {"bmp", "png"}
          and not self.color
          and self.alpha is None
      ):
          np.testing.assert_equal(img, self.img.astype(self.dtype))
  
imports: import numpy
  import tempfile
  import unittest
  from PIL import Image
  import chainer
  from chainer import testing
  from chainercv.utils import read_image
  from chainercv.utils import write_image
label_desc: Use image node_id 3 for calling the TestReadImage obj's underlying member method code with example usage: obj.test_read_image_as_grayscale() without return types