use Mapping from collections.abc

[graphaelli]

for compat with python 3.10

This already has a test that warns under python3 < .10, and fails on 3.10 with:

AttributeError: module 'collections' has no attribute 'Mapping'

[apmmachine]

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• Start Time: 2022-08-09T16:40:00.865+0000

• Duration: 35 min 30 sec

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Test	Results
Failed	0
Passed	716
Skipped	1
Total	717

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