code: function (selector, hash) {
      this.actionQueue.push(this.webdriverClient.element.bind(this.webdriverClient, selector));
      this.actionQueue.push(this._existsCb.bind(this, selector, hash));
      return this;
    }
docs: Checks if an element exists
  
  @method exists
  @param {string} selector Selector expression to find the element
  @param {string} hash Unique hash of that fn call
  @chainable