code: function (selector, attribute, expected, hash) {
      this.actionQueue.push(this.webdriverClient.element.bind(this.webdriverClient, selector));
      this.actionQueue.push(this.webdriverClient.getAttribute.bind(this.webdriverClient, attribute));
      this.actionQueue.push(this._attributeCb.bind(this, selector, hash, attribute, expected));
      return this;
    }
docs: Checks if an element has an attribute with the expected value
  
  @method attribute
  @param {string} selector Selector expression to find the element
  @param {string} attribute The attribute that should be checked
  @param {string} expected The expected text content
  @param {string} hash Unique hash of that fn call
  @chainable