Kotlin: simple Option implementation

Option.kt

sealed class Option<out A> {

    abstract fun get(): A

    object None : Option<Nothing>() {
        override fun get(): Nothing = throw NoSuchElementException("None.get")
    }

    data class Some<out A>(val value: A) : Option<A>() {
        override fun get(): A = value
    }

    fun isSome(): Boolean = this is Some
    fun isNone(): Boolean = this is None
}