Django Rest Framework field for reading a serializer but writing a primary key

gistfile1.py

class RichPrimaryKeyRelatedField(serializers.RelatedField):

    def __init__(self, serializer, *args, **kwargs):
        self.many = kwargs.get('many', False)
        self.serializer = serializer
        super(RichPrimaryKeyRelatedField, self).__init__(*args, **kwargs)

    def to_internal_value(self, data):
        try:
            return self.get_queryset().get(pk=data)
        except ObjectDoesNotExist:
            self.fail('does_not_exist', pk_value=data)
        except (TypeError, ValueError):
            self.fail('incorrect_type', data_type=type(data).__name__)

    def to_representation(self, value):
        return self.serializer(value, many=self.many).data