我有两个模型
我添加了一个掩码到一个模型，其中每个字母对应的值A，到第二个我将添加一个序列号，我需要这个字段来检查这个匹配值掩码
models.py

class EquipmentType(models.Model):
    name = models.CharField(max_length=255)
    mask = models.CharField(max_length=100)

class Equipment(models.Model):
    type = models.ForeignKey('EquipmentType', on_delete=models.CASCADE)
    sn = models.CharField(max_length=255, unique=True)
    note = models.CharField(max_length=255)
    
    def clean(self):
        mask = self.type
        regex = ''
        for char in mask:
            if char == 'N':
                regex += 'd'
            elif char == 'A':
                regex += '[A-Z]'
            elif char == 'a':
                regex += '[a-z]'
            elif char == 'X':
                regex += '[A-Z0-9]'
            elif char == 'Z':
                regex += '[-_@]'
        if not re.match(regex, self.sn):
            raise ValidationError({'serial_number': 'Invalid serial number'})

    class Meta:
        unique_together = ('sn', 'type')

serializers.py

class EquipmentSerializer(serializers.ModelSerializer):

class Meta:
    model = Equipment
    fields = '__all__'

def validate_serial_number(self, value):
    mask = self.instance.type.mask
    regex = ''
    for char in mask:
        if char == 'N':
            regex += 'd'
        elif char == 'A':
            regex += '[A-Z]'
        elif char == 'a':
            regex += '[a-z]'
        elif char == 'X':
            regex += '[A-Z0-9]'
        elif char == 'Z':
            regex += '[-_@]'
    for num in value:
        if not re.match(regex, num):
            raise serializers.ValidationError('Invalid serial number')
    return value

class EquipmentTypeSerializer(serializers.ModelSerializer):

    class Meta:
        model = EquipmentType
        fields = '__all__'

views.py

class EquipmenAPIListPagination(PageNumberPagination):
    page_size = 3
    page_size_query_param = 'page_size'
    max_page_size = 100

class EquipmentAPIList(generics.ListCreateAPIView):
    queryset = Equipment.objects.all()
    serializer_class = EquipmentSerializer
    permission_classes = (IsAuthenticatedOrReadOnly, )
    pagination_class = EquipmenAPIListPagination
    filter_backends = (filters.DjangoFilterBackend,)
    filterset_class  = EquipmentFilter      

    def post(self, request, format=None):
        data = request.data
        many = isinstance(data, list)
        serializer = EquipmentSerializer(data=request.data, many=many)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
    

class EquipmentAPIView(APIView):

    def get(self, request,  *args, **kwargs):
        pk = kwargs.get("pk", None)
        if not pk:
            w = Equipment.objects.all()
            return Response({'posts': EquipmentSerializer(w, many=True).data})
        mymodel = get_object_or_404(Equipment, pk=pk)
        serializer = EquipmentSerializer(mymodel)
        return Response(serializer.data)

    def put(self, request, *args, **kwargs):
        pk = kwargs.get("pk", None)
        if not pk:
            return Response({"error": "Method PUT not allowed"})
        try:
            instance = Equipment.objects.get(pk=pk)
        except:
            return Response({"error": "Object does not exists"})

        serializer = EquipmentSerializer(data=request.data, instance=instance)
        serializer.is_valid(raise_exception=True)
        serializer.save()
        return Response({"post": serializer.data})

    def delete(self, request, *args, **kwargs):
        pk = kwargs.get("pk", None)
        if not pk:
            return Response({"error": "Method DELETE not allowed"})
        return Response({"post": "delete post " + str(pk)})
    

class EquipmentTypeAPIList(generics.ListCreateAPIView):
    queryset = EquipmentType.objects.all()
    serializer_class = EquipmentTypeSerializer
    permission_classes = (IsAuthenticatedOrReadOnly, )
    pagination_class = EquipmenAPIListPagination
    filter_backends = (filters.DjangoFilterBackend,)
    filterset_class  = EquipmentTypeFilter

    def post(self, request, format=None):
        data = request.data
        many = isinstance(data, list)
        serializer = EquipmentTypeSerializer(data=data, many=many)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
    

class EquipmentTypeAPIView(APIView):

    def get(self, request,  *args, **kwargs):
        pk = kwargs.get("pk", None)
        if not pk:
            w = EquipmentType.objects.all()
            return Response({'posts': EquipmentTypeSerializer(w, many=True).data})
        mymodel = get_object_or_404(Equipment, pk=pk)
        serializer = EquipmentTypeSerializer(mymodel)
        return Response(serializer.data)

我这样做了，但验证不起作用。所有的数字一般都是加起来的，我该怎么修？