code: def test_heatmap_extents(self):
      hmap = HeatMap([("A", 50, 1), ("B", 2, 2), ("C", 50, 1)])
      plot = mpl_renderer.get_plot(hmap)
      assert plot.get_extents(hmap, {}) == (-0.5, -22, 2.5, 74)
  
file_path: holoviews/holoviews/tests/plotting/matplotlib/test_heatmapplot.py
imports: import numpy
  from holoviews.element import HeatMap, Image
  from .test_plot import TestMPLPlot, mpl38, mpl_renderer
label_desc: Use image node_id 2 for calling the TestHeatMapPlot obj's underlying member method code with example usage: obj.test_heatmap_extents() without return types