def for_update_sql(self, nowait=False):
        if nowait:
            return 'FOR UPDATE NOWAIT'
        else:
            return 'FOR UPDATE'
Returns the FOR UPDATE SQL clause to lock rows for an update operation.
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/db/backends/__init__.py/BaseDatabaseOperations.for_update_sql