code: def test_key_len_mismatch(self):
      try:
          self.assertEqual(self.map1_1D, self.map3_1D)
          raise AssertionError("Mismatch in map key number not raised.")
      except AssertionError as e:
          self.assertEqual(
              str(e), "HoloMaps have different numbers of keys."
          )
  
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 3 for calling the RasterMapComparisonTest obj's underlying member method code with example usage: obj.test_key_len_mismatch() without return types