docs: function getProperties (header) {
      return header.split(',').map((split) => {
          const components = split.replace(/\s+/, '').split(';');
          const priorityRegex = /^q=([0-1](\.[0-9]{1,3})?)$/;
  
          /* assign null to priority when invaild quarity values */
          return {
              lang: components[0],
              priority: components[1] ? priorityRegex.test(components[1]) ? parseFloat(components[1].split('=')[1]) : null : 1
          }
      }).filter((property) => {
          return property.priority === null ? false : bcp47.check(property.lang);
      }).sort((a, b) => {
          return a.priority < b.priority ? 1 : a.priority > b.priority ? -1 : 0;
      });
  }