Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import runpy; n=runpy.run_path('examples/software-modeling/labs/13/check.py'); x=n['Ledger'](); x.fact('F','fee','100'); x.post('BAD','F',[('receivable','100'),('revenue','-99')])
                                                                                                                             ~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "examples/software-modeling/labs/13/check.py", line 61, in post
    raise ValueError("unbalanced journal")
ValueError: unbalanced journal
