VisitRateMistFn.scala

object VisitRateMist extends MistFn with Logging {
  implicit val vmArgExt = mist.api.encoding.generic.extractor[VisitMetricsResultMessage]
  implicit val vmMetricsEnc = mist.api.encoding.generic.encoder[VisitMetricsResultMessage]
  
  override def handle: Handle = {
    withArgs(arg[VisitRateArguments])
      .withMistExtras
      .onSparkSession((args: VisitRateArguments, extras: MistExtras, spark: SparkSession) => {
        //computation
        val result: VisitMetricsResultMessage = ??? 
        result
      })
  }
}