Modificateur à Kotlin
in is "for input" - you wanna put(write) something into it (so it's a "consumer")
out is "for output" - you wanna take(read) something out of it (so it's a "producer")
If you're from Java,
<in T> is for input, so it's like <? super T> (consumer)
<out T> is for output, so it's like <? extends T> (producer)
Stockholm