Apply any necessary pre-save moderation steps to new
        comments.

def pre_save_moderation(self, sender, comment, request, **kwargs):
        """
        Apply any necessary pre-save moderation steps to new
        comments.

        """
        model = comment.content_type.model_class()
        if model not in self._registry:
            return
        content_object = comment.content_object
        moderation_class = self._registry[model]

        # Comment will be disallowed outright (HTTP 403 response)
        if not moderation_class.allow(comment, content_object, request): 
            return False

        if moderation_class.moderate(comment, content_object, request):
            comment.is_public = False