问Django Admin：“另存为新”忽略GenericForeignKey

EN

class ModelAAdmin(admin.ModelAdmin):
  save_as = True

def save_related(self, request, form, formsets, change):
    if '_saveasnew' in request.POST:
        for formset in formsets:
            if formset.__class__.__name__ == 'ModelBFormFormSet':
                instances = formset.save(commit=False)
                for instance in instances:
                    content_type = ContentType.objects.get(app_label="app", model="modelA")
                    instance.object_id = form.instance.id
                    instance.content_type = content_type
    return super(ModelAAdmin, self).save_related(request, form, formsets, change)