MutableMapping Import Error

I recently set up a new environment where Python 3.10.10 was installed. I got an ImportError when trying to import fpd.fpd_file. Apparently, the MutableMapping class was moved from collections to collections.abc in an earlier version of Python. Since fpd does not set the Python version, I thought it would be best to add a try-except line for the MutableMapping import. I'll add a PR now.