collections.MutableMapping is deprecated in Python 3.3:
DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working
In Python 3.10, it's not usable at all, so stompest does not work with py310 (reported at https://bugzilla.redhat.com/1926350)
It would be great to merge #54 and then edit the parent class of InFlightOperations to be collections.abc.MutableMapping.