code: function(slot) {
      const hbAdIdTargeting = slot.getTargeting('hb_adid');
      if (hbAdIdTargeting.length > 0) {
        const hbAdId = hbAdIdTargeting[0];
        return typeof this.prebidWinnersCache[hbAdId] !== 'undefined';
      }
      return false;
    }
docs: Decides if the GPT slot contains prebid ad impression or not.
  
  When BID_WON event is emitted adid is added to prebidWinnersCache,
  then we check if prebidWinnersCache contains slot.hb_adid.
  
  This function is optional and used only when googlePublisherTag is provided.
  
  Default implementation uses slot's `hb_adid` targeting parameter.
  
  @param slot the gpt slot