First I would consider moving to importing pan-os-python instead of pandevice for your Python scripts (reference here). From there you will find the docs here, including the syntax for AddressGroup here. It would be something like this as an example:
new_group = "new-address-group" new_group_members = [new_object_one, new_object_two] fw.add(AddressGroup(name=new_group, static_value=new_group_members)).create()
Here is a working example.
Hope that helps!