message: Remove unnecessary session creation in per_image_standardization unit test
diff: @@ -1549,12 +1549,11 @@ class PerImageWhiteningTest(test_util.TensorFlowTestCase):
  def testPreservesDtype(self):
  imgs_npu8 = np.random.uniform(0., 255., [2, 5, 5, 3]).astype(np.uint8)
  - imgs_npf16 = np.random.uniform(0., 255., [2, 5, 5, 3]).astype(np.float16)
  - with self.cached_session(use_gpu=True):
  imgs_tfu8 = constant_op.constant(imgs_npu8)
  whiten_tfu8 = image_ops.per_image_standardization(imgs_tfu8)
  self.assertEqual(whiten_tfu8.dtype, tf.uint8)
  + imgs_npf16 = np.random.uniform(0., 255., [2, 5, 5, 3]).astype(np.float16)
  imgs_tff16 = constant_op.constant(imgs_npf16)
  whiten_tff16 = image_ops.per_image_standardization(imgs_tff16)
  self.assertEqual(whiten_tff16.dtype, tf.float16)
  