I had to try a lot of different alternatives, but this worked:
headers=headers, data={'params': '{\"topic_id\": "398"}'})```
So, the answer is a combination of that prior post (which said you have to escape the quotes when you are sending from a Windows machine and Arkshine's post which says it needs to be passed as data and not as a params kwarg. What I find odd though, is I thought the whole point of the params kwarg in the Python requests module was to pass parameter information.