code: def test_raster_ellipsis_slice_value_missing(self):
      data = np.random.rand(10, 10)
      try:
          hv.Raster(data)[..., "Non-existent"]
      except Exception as e:
          if "'z' is the only selectable value dimension" not in str(e):
              raise AssertionError("Unexpected exception.")
  
imports: import numpy
  import holoviews
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 2 for calling the TestEllipsisRaster obj's underlying member method code with example usage: obj.test_raster_ellipsis_slice_value_missing() without return types