Not possible to access id of item in lense

[white-gecko]

I want to access the data filed id of an item in a lense, but it is empty.

If I take the flag demo and change the the .code to .id in the lense, I get nothing.

https://github.com/simile-widgets/exhibit/tree/master/scripted/demos/flags

<div data-ex-role="lens" style="display: none;" class="map-lens">
    <div class="flag-container">
        <img data-ex-src-subcontent="http://upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Flag_of_{{.label}}.svg/200px-Flag_of_{{.label}}.svg.png" alt="wikipedia flag image"/>
    </div>
    <div><b data-ex-content=".label"></b> [<span data-ex-content=".code"></span>]</div>
    <div>(Image from Wikipedia)</div>
</div>

change the third last line to

    <div><b data-ex-content=".label"></b> [<span data-ex-content=".id"></span>]</div>

is this the expected behavior? Is there any other way of accessing the id of an item?
(I know in this example the value of id is duplicated to code, but my source is bibsonomy json output and it has an id, which is not reproducible from any other field.

[EDIT] Actually in my case I found out, it is possible to reproduce the id from the other values, by doing concat('http://www.bibsonomy.org/bibtex/', .intraHash, '/', .user) or more precise concat('http://www.bibsonomy.org/bibtex/2', .intraHash, '/', .user)