Stuck on Creating a cart

I am using the Ultimate Django course. I am up to part 2 Designing and Implementing a Shopping Cart API. It must be me because other people have done it, but I can’t see what is wrong. Thereare only three things to do according to Mosh: Create a View, Create a Serializer and Create a Route. Three simple steps I have done too many times now with the same result. When I Post to create the empty Cart I am greeted with
create() must be implemented.

Request Method: POST
Request URL:
Django Version: 4.2.5
Exception Type: NotImplementedError
Exception Value: create() must be implemented.

Which I thought was covered by
class CartViewSet(CreateModelMixin, GenericViewSet):
queryset = Cart.objects.all()
serializer_class = CartSerializer

What have I missed?

For completeness
router.register(‘carts’, views.CartViewSet)
class CartSerializer(serializers.Serializer):

id = serializers.UUIDField(read_only=True)

class Meta:
    model = Cart
    fields = ['id']

It’s me doing it wrong again. Should be
class CartSerializer(serializers.ModelSerializer):