Using request.el question: what is function*?

[tzach . livyatan]

Hello
elisp n00b here

I'm trying to use an example of request.el

(request
 "http://httpbin.org/get";
 :params '(("key" . "value") ("key2" . "value2"))
 :parser 'json-read
 :success (function*
           (lambda (&key data &allow-other-keys)
             (message "I sent: %S" (assoc-default 'args data)))))

http://tkf.github.io/emacs-request/#examples

and getting 
request: Symbol’s function definition is void: function*

Where do function* macro(?) is coming from? The name makes it very hard to 
Google this issue.

Thanks
Tzach