In the simple test case

Observable.from_dict({'event': {'type': {'xsi:type': 'cyboxVocabs:EventTypeVocab-1.0.1', 'value': 'DHCP'} }})

I get the error message TypeError: value must be an Event for line 248 of observable.py. The line is

obs.event = Object.from_dict(observable_dict.get('event'))

However, it appears this should be Event.from_dict. The property setter for event is rejecting the non-Event output from Object.from_dict in its if not isinstance(value, Event) test.