Django Rest Framework model serializer field level validation

Question

I have a DRF ModelSerializer, and I'm trying to override the validation, to no avail.

The reason to override the validation is that the corresponding model field is a postgresql HStoreField, so effectively a python dict. However, the incoming data is an array, and I build the corresponding dict during the create function.

Model Part:

class Report(models.Model):
    report = HStoreField()

Serializer:

class ReportSerializer(serializers.ModelSerializer):
    class Meta:
        model = Report
        fields = "__all__"

    def create(self, validated_data):
        codes = validated_data.pop("report")
        report = {code: translate_code(code) for code in codes}
        return Report(**validated_data, report=report)

    def validate_report(self, value):
        print("called")
        return type(value) == type([]) # I know this is hacky

So the idea is to translate all of the codes to their respective translations, and save that as a key value pair. This is because I will always need the code and its translation together, and from a performance standpoint it makes more sense to do this once and save it in the db, rather than doing the translation on read.

tl;dr: Model field expects dict, data is actually list, I'm trying to override the validation of this field on the serializer to accept this.

Unfortunately, the validate_report function never seems to be called, and I'm not sure why.

EDIT

I also tried this:

class ReportSerializer(serializers.ModelSerializer):
    class Meta:
        model = Report
        fields = "__all__"
        validators = []

    def create(self, validated_data):
        codes = validated_data.pop("report")
        report = {code: translate_code(code) for code in codes}
        return Report(**validated_data, report=report)

    def validate(self, data):
        return isinstance(data["report"], "list")

But this validate() is not called either

EDIT: Viewset:

class ReportsViewset(viewsets.ModelViewSet):
    serializer_class = ReportSerializer
    viewset = Report.objects.all()