code: function(instanceConfig, slot, version) {
      const bid = getHighestPrebidBidResponseBySlotTargeting(
        instanceConfig,
        slot,
        version
      );
  
      // this is bid response event has `bidder` while bid won has bidderCode property
      return bid ? bid.bidderCode || bid.bidder : null;
    }
docs: If isPrebidAdImpression decides that slot contain prebid ad impression,
  this function should return prebids highest ad impression partner for that
  slot.
  
  Default implementation uses slot's `hb_adid` targeting value to find
  highest bid response and when present then returns `bidder`.
  
  @param instanceConfig merged analytics adapter instance configuration
  @param slot the gpt slot for which the name of the highest bidder shall be
  returned
  @param version the version of the prebid.js library