def save_new_tags(self, product=None):
        tags = self.cleaned_data.setdefault("tags", set())
        tags.update([int(tid) for tid in self.data.getlist("tag-tag")])

        new_tags = self.data.getlist("tag-newtag")

        for name in new_tags:
            # @@@ should pass in user here, need MTQuerySet.get_or_create
            t, created = model.Tag.objects.get_or_create(
                name=name, product=product)
            tags.add(t.id)
Save new tags and add them to the list of tags to assign.
dataset/ETHPy150Open mozilla/moztrap/moztrap/view/manage/cases/forms.py/BaseCaseForm.save_new_tags