содержит

import kotlin.math.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   val collection: Collection<Int> = listOf(1, 2, 3)

println("1 in collection is ${1 in collection}") // true
println("4 in collection is ${4 in collection}") // false

// Ref does not override equals, so instances compared by reference
class Ref<T>(val value: T)

val r0 = Ref(42)
val refCollection: Collection<Ref<Int>> = listOf(r0)

println("r0 in refCollection is ${r0 in refCollection}") // true
// Ref(42) is a new instance
println("Ref(42) in refCollection is ${Ref(42) in refCollection}") // false 
   //sampleEnd
}