Apple Script Keynote Auto-Loop

Question

Hello I'm trying to build a very simple Automator service to automatically turn on Auto Loop within a Keynote document. I'm not a very familiar with AppleScript, but I have used it a few times to do minor things. I'm gettin the following error when using this script within an automator service:

Synatax Error

"Can’t set «class aulp» to true."

Im sure it is something very obvious, but I'm not that well versed in AppleScript. Any help would be greatly appreciated.

Here is the script

on run {input}
set thisDocument to input
tell application "Keynote"

    tell thisDocument

        set auto loop to true



        save thisDocument

    end tell

end tell
end run