How to select all text items on a slide using applescript?

Question

I want to select only the text items on a slide using apple script.

tell application "Keynote"
    activate

    tell front document     

        tell slide 1
            select (every text item)
        end tell
        -- save
    end tell

end tell

I keep getting the following error:

error "Keynote got an error: every text item of slide 1 of document 1 doesn’t understand the “select” message." number -1708 from every text item of slide 1 of document 1

Any help would be much appreciated!