docs: function (selector, expected, hash) {
      this.actionQueue.push(this.webdriverClient.element.bind(this.webdriverClient, selector));
      this.actionQueue.push(this.webdriverClient.getAttribute.bind(this.webdriverClient, 'value'));
      this.actionQueue.push(this._valCb.bind(this, selector, hash, expected));
      return this;
    }