code: def test_raster_index(self):
      raster = Raster(self.array1)
      self.assertEqual(raster[0, 1], 3)
  
imports: import numpy
  from holoviews.element import HSV, RGB, Curve, Image, QuadMesh, Raster
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 3 for calling the TestRaster obj's underlying member method code with example usage: obj.test_raster_index() without return types