Today we have a Kotlin brain teaser! What does this code print?

Issue_24_Practice_Question.kt

data class Foo(val i: Int)

fun main() {
   val map = mapOf(
       1 to Foo(1),
       2 to Foo(2),
       3 to Foo(3),
   )
   
   println("map = $map")
   println("map[1] is Foo  = ${map[1] is Foo}")
   println("map[0] is Foo  = ${map[0] is Foo}")
   println("map[0] is Foo? = ${map[0] is Foo?}")
}