constructor(options = {}, xhrIo = undefined) {
    /**
     * @const
     * @private {string}
     */
    this.format_ =
        options.format || goog.getObjectByName('format', options) || 'text';

    /**
     * @const
     * @private {boolean}
     */
    this.suppressCorsPreflight_ = options.suppressCorsPreflight ||
        goog.getObjectByName('suppressCorsPreflight', options) || false;

    /**
     * @const
     * @private {boolean}
     */
    this.withCredentials_ = options.withCredentials ||
        goog.getObjectByName('withCredentials', options) || false;

    /**
     * @const {!Array<!StreamInterceptor>}
     * @private
     */
    this.streamInterceptors_ = options.streamInterceptors ||
        goog.getObjectByName('streamInterceptors', options) || [];

    /**
     * @const {!Array<!UnaryInterceptor>}
     * @private
     */
    this.unaryInterceptors_ = options.unaryInterceptors ||
        goog.getObjectByName('unaryInterceptors', options) || [];

    /** @const @private {?XhrIo} */
    this.xhrIo_ = xhrIo || null;
  }
@param {!ClientOptions=} options
@param {!XhrIo=} xhrIo