Cannot run example 'examples/calibration_CDM_irrad.yaml'

When running example 'examples/calibration_CDM_irrad.yaml', the following error message appears:

$ conda activate pyxel-dev
(pyxel-dev) $ cd pyxel/examples
(pyxel-dev) examples $ python ../pyxel/run.py -c calibration_CDM_irrad.yaml
Traceback (most recent call last):
  File "XX/pyxel/pyxel/run.py", line 296, in <module>
    main()
  File "XX/pyxel/pyxel/run.py", line 290, in main
    run(input_filename=opts.config, random_seed=opts.seed)
  File "XX/pyxel/pyxel/run.py", line 184, in run
    simulation.calibration.post_processing(calib_results=results, output=out)
  File "XX/pyxel/pyxel/calibration/calibration.py", line 788, in post_processing
    output.calibration_plots(calib_results[0][1])
  File "XX/pyxel/pyxel/util/outputs.py", line 743, in calibration_plots
    self.champions_plot(
  File "XX/pyxel/pyxel/util/outputs.py", line 661, in champions_plot
    self.plot_graph(x=generations, y=column, args=plt_args)
  File "XX/pyxel/pyxel/util/outputs.py", line 420, in plot_graph
    user_plt_args_dct = self.user_plt_args.to_dict()
AttributeError: 'dict' object has no attribute 'to_dict'