docs: function groupTags(tags, key) {
      var groupBy = 'data-combo';
      return tags.reduce(function (previous, current) {
          var combineName = current.attributes[groupBy];
          var keyValue = current.attributes[key];
  
          if (!keyValue || !combineName) {
              return previous;
          }
  
          var group = previous[combineName];
  
          if (!group) {
              group = previous[combineName] = [];
          }
  
          delete current.attributes[groupBy];
          group.push(current);
  
          return previous;
      }, {});
  }