Maybe use coverage package?

As the original trace.py author, I'm flattered that you are using it under the covers, but I'm also mildly surprised you've not moved on to Ned Batchelder's coverage package. I don't know the details of either package, so maybe you've deemed it not a big enough gain to use.

Start by reading trace.py and comparing its current role with Ned Batchelder's coverage package. The issue does not specify a target behavior or acceptance criteria, so first establish whether coverage can replace the existing implementation and what completion would mean.

Written by the indexing model from the issue text.