code: def setUp(self):
      super().setUp()
      # Two overlays of depth two with different layers
      self.overlay1_depth2 = self.mat1 * self.mat2
      self.overlay2_depth2 = self.mat1 * self.mat3
      # Overlay of depth 2 with different bounds
      self.overlay3_depth2 = self.mat4 * self.mat5
      # # Overlay of depth 3
      self.overlay4_depth3 = self.mat1 * self.mat2 * self.mat3
  
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 1 for calling the RasterOverlayTestCase obj's underlying member method code with example usage: obj.setUp() without return types