How to filter a serializer manytomany field in djangorestframework

I want to filter the manytomany field based on the current instance selected field[‘customer’]. I want the cart_items manytomany field to only contain the cart_items of the selected customer in cart API.

models.py

class Product(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    product_id = ShortUUIDField(unique=True, editable=False)
    name = models.CharField(max_length=100)
    # price = MoneyField(max_digits=14, decimal_places=2)
    price = models.DecimalField(max_digits=14, decimal_places=2)


class Customer(models.Model):
    customer_id = ShortUUIDField()
    user = models.ForeignKey(User, on_delete=models.DO_NOTHING)
    name = models.CharField(max_length=255, blank=False)
    email = models.EmailField(unique=True)


class CartItems(models.Model):
    cart_items_id = ShortUUIDField()
    user = models.ForeignKey(User, on_delete=models.DO_NOTHING)
    customer = models.ForeignKey(Customer, on_delete=models.DO_NOTHING)
    products = models.ForeignKey(Product, on_delete=models.DO_NOTHING)
    quantity = models.IntegerField(default=1)

    class Meta:
        unique_together = (
            ("customer", "user", "products"),
        )

class Cart(models.Model):
    cart_id = ShortUUIDField()
    user = models.ForeignKey(User, on_delete=models.DO_NOTHING)
    customer = models.ForeignKey(Customer, on_delete=models.DO_NOTHING)
    cart_items = models.ManyToManyField(CartItems)

serializers.py

class CartSerializer(serializers.ModelSerializer):

    class Meta:
        model = models.Cart
        fields = '__all__'
        read_only_fields = ['user']

I have tried to use all of the things below. Any help would be appreciated.
Requirement:
The cart_items must contain items of the selected customer only.

class CartSerializer(serializers.ModelSerializer):
    """serializer for Product objects."""
    # authors = serializers.PrimaryKeyRelatedField(queryset=Author.objects.all(), many=True)

    # cart_items = serializers.PrimaryKeyRelatedField(queryset=models.CartItems.objects.filter(customer=self.context['request'].user), many=True)
    # cart_items = serializers.PrimaryKeyRelatedField(queryset=models.CartItems.objects.filter(user=2), many=True)
    # cart_items = CustomerFilteredPrimaryKeyRelatedField(many=True, source='user.Customer')

    # cart_items = serializers.PrimaryKeyRelatedField('get_cart')
    #
    # def get_cart(self, product):
    #     qs = models.CartItems.objects.filter(user=2)
    #     serializer = CartItemSerializer(instance=qs, many=True)
    #     return serializer.data

    class Meta:
        model = models.Cart
        fields = '__all__'
        read_only_fields = ['user']

# views.py
class CartView(GenericAPIView, ListModelMixin):
    ... # Don't pass queryset attr here
    
    serializer_class = CartSerializer
    
    def get_queryset(self):
        user = self.request.user
        queryset = Cart.objects.prefetch_related('cart_items').filter(user=user)
        # If you aren't changing your model, you could get the customer as:
        # customer = Customer.objects.get(user=user)
        # queryset = Cart.objects.prefetch_related('cart_items').filter(customer=customer) 
        return queryset

def get_queryset(self):
    customer_id = self.request.query_params.get('customer_id')
    # You could include the merchant user in the filter too, but I guess the customer filter would already narrow it down.
    queryset = Cart.objects.prefetch_related('cart_items__customer').filter(cart_items__customer_id=customer_id)
    return queryset