django rest framework如何实现nest field显示，如何保存有外键的字段更新

class VersionPoolSerializer(serializers.ModelSerializer):
    site_name = serializers.ReadOnlyField(source='site_name.name')
    dep_version = DeployPoolSerializer(many=True, required=False, read_only=True)
    create_user = serializers.ReadOnlyField(source='create_user.username')

    class Meta:
        model = VersionPool
        fields = ('id', 'name', 'site_name', 'dep_version', 'create_user', 'add_date')

class VersionPoolViewSet(viewsets.ModelViewSet):
    """
    This viewset automatically provides `list`, `create`, `retrieve`,
    `update` and `destroy` actions.

    Additionally we also provide an extra `highlight` action.
    """
    queryset = VersionPool.objects.all()
    serializer_class = VersionPoolSerializer
    authentication_classes = (TokenAuthentication,)
    paginate_by = 10

    def get_queryset(self):
        print (self.request.user, '##################')
        print(self.request.auth, '##################')
        queryset = self.queryset
        return queryset

    def create(self, request, *args, **kwargs):
        name = request.data['name']
        site_name = request.data['site_name']
        validated_data = dict()
        validated_data['name'] = site_name + "-" + name
        validated_data['site_name'] = Site.objects.get(name=site_name)
        validated_data['create_user'] = request.user
        try:
            VersionPool.objects.create(**validated_data)
            response_data = {
                'name': site_name + "-" + name,
                'create_user': request.user.username,
                'message': 'version item save success.'
            }
            return Response(response_data, status=status.HTTP_201_CREATED)
        except:
            response_data = {
                'name': site_name + "-" + name,
                'create_user': request.user.username,
                'message': 'version item save failed.'
            }
            return Response(response_data, status=status.HTTP_400_BAD_REQUEST)