code: function parallel(inst, elems, argv, event, fin, _postSequence) {
      var total = elems.length;
      var complete = 0;
      function check(err, list) {
          if (total === ++complete) {
              if (!_isFunc(list)) return _postSequence(list, fin);
              return fin(err, list);
          }
      }
      for (var i = 0; i < total; i++) {
          if (_isList(elems[i])) {
              var after = edit(inst, elems, i, argv, event, check);
              branch(inst, elems[i], argv, event, after);
          }
          else {
              check(null, elems);
          }
      }
  }
docs: Run the sequence in parallel