How to use :nth-of-type()

`NSError *xmlError;
ONOXMLDocument *document = [ONOXMLDocument HTMLDocumentWithData:data error:&xmlError];
ONOXMLElement *element = [document.rootElement firstChildWithCSS:@"table:nth-of-type(2)"];`


XPath error : Invalid expression
.//table:nth-of-type(2)
                    ^
