code: def test_element_mismatch(self):
      try:
          self.assertEqual(self.overlay1_depth2, self.overlay2_depth2)
      except AssertionError as e:
          if not str(e).startswith(
              "Image not almost equal to 6 decimals\n"
          ):
              raise self.failureException(
                  "Image mismatch error not raised."
              )
  
imports: import numpy
  from holoviews import Image
  from holoviews.core import BoundingBox, Dimension
  from holoviews.core.element import HoloMap
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 2 for calling the RasterOverlayComparisonTest obj's underlying member method code with example usage: obj.test_element_mismatch() without return types