code: def test_image_listed_cmap(self):
      colors = ["#ffffff", "#000000"]
      img = Image(np.array([[0, 1, 2], [3, 4, 5]])).opts(cmap=colors)
      plot = mpl_renderer.get_plot(img)
      artist = plot.handles["artist"]
      cmap = artist.get_cmap()
      self.assertIsInstance(cmap, ListedColormap)
      assert cmap.colors == colors
  
file_path: holoviews/holoviews/tests/plotting/matplotlib/test_rasterplot.py
imports: from unittest import SkipTest
  import numpy
  from matplotlib.colors import ListedColormap
  from holoviews.element import Image, ImageStack, Raster
  from holoviews.plotting.mpl.raster import RGBPlot
  from .test_plot import TestMPLPlot, mpl_renderer
label_desc: Use image node_id 5 for calling the TestRasterPlot obj's underlying member method code with example usage: obj.test_image_listed_cmap() without return types