```fun main(args: Array<String>) { val s...
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fun main(args: Array<String>) {
    val set  = EnumSet.of(PackageFlags.IS_DEBUGGABLE, PackageFlags.IS_DATA_ONLY)
    println(set.mask)
}

val EnumSet<PackageFlags>.mask get() = fold(0, {acc, flag -> acc or flag.mask})