How do I display "image X of Y" in a Lightroom web engine Lua template?

I'm creating a new "web engine" (i.e. gallery format) for Lightroom, which uses Lua templates to generate HTML for the gallery pages.

I've got both the SDK and Programmers Guide from here: http://www.adobe.com/devnet/photoshoplightroom/

But none of the SDK docs, examples, nor the Programmers Guide give me any hint of what variables I need to use to add, for example, "image 1 of 50" to the page heading.

There are a couple of objects, $m开发者_JAVA百科odel and $image which I suspect will have this information in - is there a way to dump the full data contained within these as text/html, so I can output to the HTML page and figure out what variable I want?

Update: half way there... found the variable $index which provides the current image number, so now I just need to figure out what/where the total count variable is.

On page 133 of the guide pdf it lists the variable "numImages". Is that what you need?