async send(notification, msg, monitorJSON = null, heartbeatJSON = null) {
        const okMsg = "Sent Successfully.";
        const url = "https://www.pushplus.plus/send";
        try {
            const config = {
                headers: {
                    "Content-Type": "application/json",
                },
            };
            const params = {
                "token": notification.pushPlusSendKey,
                "title": this.checkStatus(heartbeatJSON, monitorJSON),
                "content": msg,
                "template": "html"
            };
            await axios.post(url, params, config);
            return okMsg;
        } catch (error) {
            this.throwGeneralAxiosError(error);
        }
    }
@inheritdoc
@param {BeanModel} notification Notification object
@param {string} msg Message content
@param {?object} monitorJSON Monitor details
@param {?object} heartbeatJSON Heartbeat details
@returns {Promise<string>} Success message