I cannot search a field when i added a serializermethod in documentviewset

Question

class VariantSerializers(DocumentSerializer):
    uom = serializers.SerializerMethodField('get_uom')

    def get_uom(request,obj):
        if obj.uom_id is not None:
            uomData = Uom.objects.filter(code=obj.uom_id).first()
        if uomData is None:
            return obj.uom_id
        return uomData.name
    class Meta:
        model = Variant
        document = VariantDoc
        fields = '__all__'

Here i added a serializermethod and here i cannot search with uom name but it's not working