Can you help understand averageCarrierDelay?

[asarkar]

val averageCarrierDelay =
    Flow[FlightDelayRecord]
      .groupBy(30, _.uniqueCarrier)
      .fold(("", 0, 0)) {
        (x: (String, Int, Int), y: FlightDelayRecord) =>
          val count = x._2 + 1
          val totalMins = x._3 + Try(y.arrDelayMins.toInt).getOrElse(0)
          (y.uniqueCarrier, count, totalMins)
      }.mergeSubstreams

What's the Tuple3[String, Int, Int]? Where does it come from in the flow?

[asarkar]

Never mind, got it. Tuple3[String, Int, Int] is the zero in fold[T](zero: T)(f: (T, Out) ⇒ T): Repr[T]. It doesn't come from elsewhere in the flow.