Error on python>=3.10

[PaoloAlbano]

Description

error running target-csv on a python version >=3.10.

Enviroment:
output of uname -a:
Linux 41bfd29a1839 5.15.49-linuxkit #1 SMP PREEMPT Tue Sep 13 07:51:32 UTC 2022 aarch64 GNU/Linux

output of python -V
Python 3.11.1

i'm working with docker hub image: python:3.11-slim

Problem

Starting from python 3.10, MutableMapping was moved under collections.abc .

See:
Deprecated since version 3.3, will be removed in version 3.10: Moved [Collections Abstract Base Classes](https://docs.python.org/3.9/library/collections.abc.html#collections-abstract-base-classes) to the [collections.abc](https://docs.python.org/3.9/library/collections.abc.html#module-collections.abc) module. For backwards compatibility, they continue to be visible in this module through Python 3.9.

Reference: https://docs.python.org/3.9/library/collections.html

[frasermarlow]

I am running on Python 3.10.9. with a modified target_csv.py modified with

from collections.abc import MutableMapping

and the updated function

def flatten(d, parent_key='', sep='__'):
    items = []
    for k, v in d.items():
        new_key = parent_key + sep + k if parent_key else k
        if isinstance(v, MutableMapping):
            items.extend(flatten(v, new_key, sep=sep).items())
        else:
            items.append((new_key, str(v) if type(v) is list else v))
    return dict(items)

And it's working fine so far.