def __iter__(self):
    raise NotImplementedError()
Backends can implement as needed to re-enable foreign key constraint
dataset/ETHPy150Open GoogleCloudPlatform/appengine-mapreduce/python/src/mapreduce/datastore_range_iterators.py/AbstractKeyRangeIterator.__iter__--crossover with--dataset/ETHPy150Open django/django/django/db/backends/base/base.py/BaseDatabaseWrapper.enable_constraint_checking