code:

    val featureMap = FeatureMapBuilder()
      .add(AccountAgeFeature, query.getOptionalUserId.flatMap(SnowflakeId.timeFromIdOpt))
      .add(ClientIdFeature, query.clientContext.appId)
      /**
       * These author ID lists are used purely for metrics collection. We track how often we are
       * serving Tweets from these authors and how often their tweets are being impressed by users.
       * This helps us validate in our A/B experimentation platform that we do not ship changes
       * that negatively impacts one group over others.
       */
      .add(DDGStatsDemocratsFeature, ddgStatsAuthors.longSeq(Democrats).toSet)
      .add(DDGStatsRepublicansFeature, ddgStatsAuthors.longSeq(Republicans).toSet)
      .add(DDGStatsVitsFeature, ddgStatsAuthors.longSeq(Vits).toSet)
      .add(DDGStatsElonFeature, ddgStatsAuthors.longValue(Elon))