code: function doBidderSync(type, url, bidder, done) {
    if (!url) {
      utils.logError(`No sync url for bidder "${bidder}": ${url}`);
      done();
    } else if (type === 'image' || type === 'redirect') {
      utils.logMessage(`Invoking image pixel user sync for bidder: "${bidder}"`);
      utils.triggerPixel(url, done);
    } else if (type == 'iframe') {
      utils.logMessage(`Invoking iframe user sync for bidder: "${bidder}"`);
      utils.insertUserSyncIframe(url, done);
    } else {
      utils.logError(`User sync type "${type}" not supported for bidder: "${bidder}"`);
      done();
    }
  }
docs: Run a cookie sync for the given type, url, and bidder
  
  @param {string} type the type of sync, "image", "redirect", "iframe"
  @param {string} url the url to sync
  @param {string} bidder name of bidder doing sync for
  @param {function} done an exit callback; to signify this pixel has either: finished rendering or something went wrong