AppleScript script for exporting only iCloud contacts

Question

I wrote this AppleScript script, below, which extracts all contacts. How do I extract only the ones from iCloud?

set desktopPath to (path to the desktop folder as string) & "contactBackup"
alias desktopPath

tell application "Contacts"
    repeat with cardPerson in people
        set nameOfvCard to name of cardPerson & ".vcf"
        set outFile to (open for access file (desktopPath & ":" & nameOfvCard) with write permission)
        write (vcard of cardPerson as text) to outFile
        close access outFile
    end repeat
end tell