def session():
session = Session()
# We want the session be flushed and commited after each instance
# to not violate FK constraints in DB
def add_all(self, instances):
for instance in instances:
self.add(instance)
self.flush()
self.expunge(instance)
# Override the originial add_all for this session
session.add_all = add_all.__get__(session, Session)
return session
