How to set keynote all slides background fill format to no fill ?

Hi,

I try to export keynote slides to Pngs, is there a way to set all slides background to “no fill”, which is good for pngs.


tell application "Keynote"
	set doc to open docFile
--    How to set all slides background fill format to no fill ?
	export doc as slide images to file targetFolderHFSPath with properties {image format:PNG}
end tell


Thanks,