in scala-repl/src/main/scala/spark/ztools.sc [744:748]
private def isUnitOrNullResult(result: mutable.Map[String, Any], name: String) = {
val res = result(name).asInstanceOf[mutable.Map[String, Any]]
val valType = res(ResNames.TYPE)
valType == "Unit" || valType == "Null"
}