With dropping python 3.7 it's possible to remove a py-37-specific workorund in thePicklePersistence implementation. More details can be foundhere. We should revisit that implementation and remove all python-3.7 specific code. The corresponding test cases also needs to be adapted to drop any python 3.7 related clauses.

A PR in this direction is very welcome. As long as#3728 is open, it should be based on thedrop-py-37 branch. If you would like to send a PR, please be sure to read ourcontribution guide and leave a short comment so that we can assign you.