Correct field to use in Admin form when multi=True

Although there's stuff in the README about custom forms and the custom widgets, I couldn't see anything about what to do if you're using multi=True. I've got it working, but I'm not sure if this is the best way.

I have this model:

from django.db import models
from django_countries.fields import CountryField

class Person(models.Model):
    countries = CountryField(multiple=True, blank=True)

And then in admin.py:

from django import forms
from django.contrib.admin.widgets import FilteredSelectMultiple
from django_countries import countries as countries_object
from .models import Person

class PersonForm(forms.ModelForm):
    class Meta:
        model = Person
        exclude = ()

    countries = forms.MultipleChoiceField(
        choices=list(countries_object),
        widget=FilteredSelectMultiple("countries", is_stacked=False),
        required=False,
    )

The choices is the bit I'm least sure about.

If it is the best way then maybe something could be added to the README to help the next person who's confused?

SmileyChris / django-countries

Correct field to use in Admin form when multi=True #388