def help_center_article_subscriptions(self, article_id, locale=None, **kwargs):
        "https://developer.zendesk.com/rest_api/docs/help_center/subscriptions#list-article-subscriptions"
        api_path = "/api/v2/help_center/articles/{article_id}/subscriptions.json"
        api_path = api_path.format(article_id=article_id)
        if locale:
            api_opt_path = "/api/v2/help_center/{locale}/articles/{article_id}/subscriptions.json"
            api_path = api_opt_path.format(article_id=article_id, locale=locale)
        return self.call(api_path, **kwargs)
https://developer.zendesk.com/rest_api/docs/help_center/subscriptions#list-article-subscriptions