Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import runpy; n=runpy.run_path('examples/software-modeling/labs/19/check.py'); n['Period'](10,10)
                                                                                   ~~~~~~~~~~~^^^^^^^
  File "<string>", line 5, in __init__
  File "examples/software-modeling/labs/19/check.py", line 14, in __post_init__
    raise ValueError("invalid UTC teaching-day period")
ValueError: invalid UTC teaching-day period
