arrow-core-data / arrow.core / flatten
flatten
fun <A, B> Either<A, Either<A, B>>.flatten(): Either<A, B>
fun <A, B> Ior<A, Ior<A, B>>.flatten(SA: Semigroup<A>): Ior<A, B>
fun <A> NonEmptyList<NonEmptyList<A>>.flatten(): NonEmptyList<A>
fun <A> Option<Option<A>>.flatten(): Option<A>