Does not handle nullable values

[headinthebox]

@Serializable data class Bar( val x: Int, val y: Int? = null, val z: Int? )

println(pprint(Bar(x = 3, z = null)).plainText) ==> Bar(x = 3, null, null)

would expect

Bar(x = 3, z = null), or perhaps Bar(x = 3, y = null, z = null)