declare abstract class Base_sms<O> {
    protected opt: O;
    constructor(opt: O);
    /**
     * Send sms
     * @param ccode - calling code
     * @param phone - phone number
     * @param content - sms text content
     * @param opt
     */
    abstract send(ccode: string, phone: string, content: string | object, opt: any): Promise<any>;
    /**
     * Verify this.opt
     *
     * throws if invalid
     */
    abstract validate_opt(): true;
}

export { Base_sms };