def date_trunc_sql(self, lookup_type, field_name):
        raise NotImplementedError()
Return the member technologies of a group. If ``in_model`` is
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/db/backends/__init__.py/BaseDatabaseOperations.date_trunc_sql--crossover with--dataset/ETHPy150Open calliope-project/calliope/calliope/core.py/Model.get_group_members