'Return all the incomplete events, in order.'

def incomplete(self, **filters):

    if ('event_id' in filters):
        ids = [filters['event_id']]
    else:
        ids = sorted(self._events.keys())
    for ek in ids:
        e = self._events.get(ek, None)
        if ((e is not None) and (Event.COMPLETE not in e.flags) and self._match(e, filters)):
            (yield e)
