code: def test_identities(self):
      g = Image.linear_gradient("L")
      im = Image.merge(
          "RGB",
          [
              g,
              g.transpose(Image.Transpose.ROTATE_90),
              g.transpose(Image.Transpose.ROTATE_180),
          ],
      )
  
      # Fast test with small cubes
      for size in [2, 3, 5, 7, 11, 16, 17]:
          assert_image_equal(
              im,
              im._new(
                  im.im.color_lut_3d(
                      "RGB",
                      Image.Resampling.BILINEAR,
                      *self.generate_identity_table(3, size),
                  )
              ),
          )
  
      # Not so fast
      assert_image_equal(
          im,
          im._new(
              im.im.color_lut_3d(
                  "RGB",
                  Image.Resampling.BILINEAR,
                  *self.generate_identity_table(3, (2, 2, 65)),
              )
          ),
      )
  
imports: from __future__ import annotations
  from array import array
  import pytest
  from PIL import Image, ImageFilter
  from .helper import assert_image_equal
label_desc: Use image node_id 6 for calling the TestColorLut3DCoreAPI obj's underlying member method code with example usage: obj.test_identities() without return types