@JvmName("flatMapIterable") fun <T, R> Sequence<T>.flatMap(
    transform: (T) -> Iterable<R>
): Sequence<R>

fun <T, R> Sequence<T>.flatMap(
    transform: (T) -> Sequence<R>
): Sequence<R>

Returns a single sequence of all elements from results of transform function being invoked on each element of original sequence.

The operation is intermediate and stateless.

import kotlin.test.*

fun main(args: Array<String>) {
//sampleStart
val list = listOf("123", "45")
println(list.flatMap { it.toList() }) // [1, 2, 3, 4, 5]
//sampleEnd
}