code: function(syncOptions, serverResponses) {
      const syncs = [];
      utils._each(serverResponses, function(bidResponse) {
        utils._each(bidResponse.body.syncs, function(sync) {
          if (syncOptions.pixelEnabled && sync.type == 'image') {
            syncs.push({
              type: sync.type,
              url: sync.url
            });
          } else if (syncOptions.iframeEnabled && sync.type == 'iframe') {
            syncs.push({
              type: sync.type,
              url: sync.url
            });
          }
        });
      });
      return syncs;
    }
docs: Register the user sync pixels which should be dropped after the auction.
  
  @param {SyncOptions} syncOptions Which user syncs are allowed?
  @param {ServerResponse[]} serverResponses List of server's responses.
  @return {UserSync[]} The user syncs which should be dropped.