in src/main/scala/com/gu/commercial/display/AdTargetParam.scala [192:195]
def from(item: Content, surgeLookup: SurgeLookupService): Option[SurgeLevelParam] = {
val surgeLevels = bucket(surgeLookup.pageViewsPerMinute(item.id)).map(_.toString).toSet
MultipleValues.fromRawValues(surgeLevels) map (SurgeLevelParam(_))
}