val json = Json.arr(
        Json.obj("f1" -> "arr 1", "f2" -> "a"), // fail on f2 as its a string
        Json.obj("f1" -> "arr 2", "f2" -> 2),
        Json.obj("f1" -> "arr 3", "f2" -> "c"),
        Json.obj("f1" -> "arr 4", "f2" -> "d"),