// WITH_RUNTIME
// INTENTION_TEXT: "Replace with 'mapIndexed{}.flatMap{}.firstOrNull{}'"
// INTENTION_TEXT_2: "Replace with 'asSequence().mapIndexed{}.flatMap{}.firstOrNull{}'"
fun foo(list: List<String>): String? {
    <caret>return list
        .asSequence()
        .mapIndexed { index, s -> s.lines().take(index) }
        .flatMap { it.asSequence() }
        .firstOrNull { it.isNotBlank() }
}