Adding delete from cache when deleting an item from remote service

When sending a delete on an item to a service also ensure that object is not in the cache.  It can happen that items are deleted and desired to be gone but are cached for even days and require manual intervention to clean the cache.
I feel like I must be reading this wrong, because I keep seeing the `not in` as meaning "If the request was NOT a DELETE, then call `self.cache.delete`." Am I inverted, or is the conditional inverted?