def date_extract_sql(self, lookup_type, field_name):
        raise NotImplementedError()
Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/db/backends/__init__.py/BaseDatabaseOperations.date_extract_sql