docs: function combineHeaders(...args) {
    const combinedLower = {};
    const combined = {};
    args.reverse();
    args.forEach((headers) => {
      if (headers) {
        Object.keys(headers).forEach((name) => {
          const nameLower = name.toLowerCase();
          if (!hasOwnProperty.call(combinedLower, nameLower)) {
            combinedLower[nameLower] = true;
            combined[name] = headers[name];
          }
        });
      }
    });
    return combined;
  }