docs: function getInstance(options) {
    var bucket = options.bucket;
    var upyunInstance = instances[bucket];
  
    // If can not found instance, then new one.
    if (!upyunInstance) {
      instances[bucket] = upyunInstance = new UPYUN(options.bucket, options.operator, options.password, options.endpoing, options.apiVersion);
    }
  
    return upyunInstance;
  }