docs: function (query, items) {
              var sortExpressions = query.query.sort,
                  self = this;
  
              if(sortExpressions){
                  return items.sort(function (a, b) {
                      var sortExpression,
                          ret = 0;
                      for (var i = 0; i < sortExpressions.length; i++) {
                          sortExpression = sortExpressions[i];
                          ret = self._compareExpression(a, b, sortExpression);
                          if (ret !== 0) {
                              return ret;
                          }
                      }
                      return ret;
                  });
              } else {
                  return items;
              }
  
          }