code: def test_feature_with_dummy():
      feature = FeatureSpec("some kind", "some name")
      expect = feature.as_dict()
      assert (feature + DummySpec()).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 5 for calling a global function with example usage: test_feature_with_dummy() without return types