def get_loaded_field_names_cb(self, target, model, fields):
        target[model] = set([f.name for f in fields])
Set `a` can unsafe convert to `b` and `b` can unsafe convert to `a`
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/db/models/sql/query.py/Query.get_loaded_field_names_cb--crossover with--dataset/ETHPy150Open numba/numba/numba/typeconv/typeconv.py/TypeCastingRules.unsafe_unsafe