def _cache_control__get(self):
        env = self.environ
        value = env.get('HTTP_CACHE_CONTROL', '')
        cache_header, cache_obj = env.get('webob._cache_control', (None, None))
        if cache_obj is not None and cache_header == value:
            return cache_obj
        cache_obj = CacheControl.parse(value,
                                       updates_to=self._update_cache_control,
                                       type='request')
        env['webob._cache_control'] = (value, cache_obj)
        return cache_obj
Get/set/modify the Cache-Control header (`HTTP spec section 14.9
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/webob-1.2.3/webob/request.py/BaseRequest._cache_control__get