serializer.field.AttrKeyRelatedField.py

class AttrKeyRelatedField(PrimaryKeyRelatedField):
    def __init__(self, **kwargs):
        self.attr_field = kwargs.pop('attr_field')
        super(AttrKeyRelatedField, self).__init__(**kwargs)

    def use_pk_only_optimization(self):
        return False

    def to_internal_value(self, data):
        if self.pk_field is not None:
            data = self.pk_field.to_internal_value(data)
        try:
            filter_ = {self.attr_field: data}
            return self.get_queryset().get(**filter_)
        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 value
        

class MsServerSerializer(serializers.Serializer):
    client_type = AttrKeyRelatedField(queryset=ExtSystemClient.objects.all(),
                                      pk_field=CharField(),
                                      attr_field='client_type')