Reading the timeout value for a django cache entry (for testing)

[guettli]

We had a bug in our production system. The timeout was set incorrectly.

Now I want to write a test which checks, that the value of the timeout is correct.

I look at the docs and don't see a way to **read** the timeout value of a particular cache-key:

https://docs.djangoproject.com/en/2.2/topics/cache/

How could I test that the timeout value in my test is correct?