def cancel_interest(self, trainer):
        get_db().delete("workshop_trainers",
            where="workshop_id=$self.id AND trainer_id=$trainer.id",
            vars=locals())
Testing creation from HEX.
dataset/ETHPy150Open anandology/broadgauge/broadgauge/models.py/Workshop.cancel_interest--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/contrib/gis/geos/tests/test_geos.py/GEOSTest.test01f_create_hex