code: function run(element, cb) {
      return function level(error, content) {
        debug('Traversing children of element %s', element.name);
  
        if (sync) {
          return traverser(element, content, cb)();
        }
  
        setImmediate(traverser(element, content, cb));
      }
    }
docs: Traverse children of current element.
  
  @param {Object} element Properties
  @param {Function} cb Completion callback
  @api private