code: def test_rgb_ellipsis_slice_value_missing(self):
      rgb = hv.RGB(np.random.rand(10, 10, 3))
      try:
          rgb[..., "Non-existent"]
      except Exception as e:
          if str(e) != repr(
              "'Non-existent' is not an available value dimension"
          ):
              raise AssertionError("Incorrect exception raised.")
  
imports: import numpy
  import holoviews
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 6 for calling the TestEllipsisRaster obj's underlying member method code with example usage: obj.test_rgb_ellipsis_slice_value_missing() without return types