src.kt

val obj = obj {
  "key" to 3.4
  "anotherKey" to arr["test", "test2", 1, 2.433, true]
  "nullValue" to null
  "emptyObject" to obj { }
  "emptyArray" to arr
  "custom" to ZonedDateTime.now()
}

println(obj) // 1
println(obj.pretty()) // 2