Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import runpy; n=runpy.run_path('examples/software-modeling/labs/14/check.py'); x=n['book']('general'); x.implement('MISSING',1,n['Period'](10,11))
                                                                                                           ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "examples/software-modeling/labs/14/check.py", line 101, in implement
    raise ValueError("no active commitment")
ValueError: no active commitment
