How to serialize django model using serpy?

Kinda new to python and django so I apologize if this is a noobish question. How would I serialize this following related models using Serpy instead of DRF ModelSerializer and then use the serpy serializer in a DRF ModelViewSet?

Models:

class Person(models.Model):
    first_name = models.CharField(_("First Name"), max_length=128, null=True)
    middle_name = models.CharField(_("Middle Name"), max_length=128, blank=True, null=True)
    last_name = models.CharField(_("Last Name"), max_length=128, null=True)
    email = models.EmailField(_("Email"), blank=True, null=True)

    def __unicode__ (self):
        return '%s: %s %s %s' % (self.id, self.first_name, self.middle_name, self.last_name)

class Bookmark(models.Model):
    person = models.ForeignKey(Person, related_name='bookmarks', on_delete=models.CASCADE)
    title = models.CharField(_("Title"), max_length=9999, blank=True, null=True)
    url = models.URLField(_("Url"), max_length=9999, blank=True, null=True)

    def __unicode__ (self):
        return '%s %s' % (self.title, self.url)

DRF ModelSerializers:

class BookmarkSerializer(ModelSerializer):
    class Meta:
        model = Bookmark
        fields = ('id', 'title', 'url', 'person')

class PersonSerializer(ModelSerializer):
    bookmarks = BookmarkSerializer(many=True, read_only=True)

    class Meta:
        model = Person
        fields = ('id', 'first_name', 'middle_name', 'last_name', 'email', 'bookmarks')

DRF ModelViewSet:

class PersonViewSet(viewsets.ModelViewSet):
    queryset = Person.objects.all()
    serializer_class = PersonSerializer

[ahankinson]

Ah. Try:

bookmarks = BookmarkSerializer(many=True, attr="bookmarks.all", call=True)

[edouarobin]

Hmm seemed to get passed that, now getting the following when I try to view my persons:

AttributeError: 'NoneType' object has no attribute 'last_name'

I’m not sure if I’m allowed to use DRF ModelViewSet with serpy?

Thank you for your help btw Andrew.

Set required=False