code: def test_plot_with_dummy():
      plot = gg.ggplot()
      expect = plot.as_dict()
      assert (plot + DummySpec()).as_dict() == expect
      assert (DummySpec() + plot).as_dict() == expect
  
file_path: lets-plot/python-package/test/plot/test_assembly.py
imports: import lets_plot
  from lets_plot.plot.core import DummySpec, FeatureSpecArray
  from lets_plot.plot.core import FeatureSpec
  from lets_plot.plot.core import LayerSpec
  from lets_plot.plot.geom import _geom
  from lets_plot.plot.scale import _scale
label_desc: Use image node_id 6 for calling a global function with example usage: test_plot_with_dummy() without return types