Updating a Django queryset with annotation and subquery

I wrote this solution the first time as an answer to a question on Stack Overflow.<p><a href="https:&#x2F;&#x2F;stackoverflow.com&#x2F;a&#x2F;50134728&#x2F;755343" rel="nofollow">https:&#x2F;&#x2F;stackoverflow.com&#x2F;a&#x2F;50134728&#x2F;755343</a>