There are multiple ways to go about this, since collections.abc was introduced in Python 3.3 we don't need to worry about backporting (we only support Python 3.6+). We could
1. Replacing all collections with collections.abc (https://github.com/Sage-Bionetworks/synapsePythonClient/pull/745)
2. import the Callable (e.g from collections.abc import Mapping
This was merged and is part of the 2.1 RC.