Fix deprecated import: collections.Mapping to work on 3.10

There is an issue with collections.Mapping when using python 3.10.

When investigating the root cause, we can see a warning on previous versions:

Using or importing the ABCs from 'collections' instead "
                      "of from 'collections.abc' is deprecated since Python 3.3,"
                      "and in 3.9 it will stop working",

Fix: use collections.abc.Mapping instead.