I think he means putting a multi-line string at the end of a long line.

```scala
def this() = {
  val configString = """
    akka.loglevel = DEBUG
    akka.actor.debug {
      receive = on
      lifecycle = on
    }
    akka.event-handlers = ["akka.testkit.TestEventListener"]
  """
  this(ActorSystem("TestClientActor", ConfigFactory.parseString(configString)))
}
```