from django.contrib.admin.util import NestedObjects
from django.db import DEFAULT_DB_ALIAS
from django.core import serializers


# flatten function
def flatten(xs):
    result = []
    if isinstance(xs, (list, tuple)):
        for x in xs:
            result.extend(flatten(x))
    else:
        result.append(xs)
    return result


# parcours des objets concernés
obj =  Company.objects.get(pk=XX)
collector = NestedObjects(using=DEFAULT_DB_ALIAS)
collector.collect([obj])
datas = collector.nested()
data = flatten(datas[1])


# serialisation 
with open("export_xx.xml", "w") as out:
    xml_serializer.serialize(data, stream=out)



# deserialisation
file = open("your_file.py", "r")
data = file.read()
for obj in serializers.deserialize("xml", data):
    obj.save()