code: function sortBy($column, event) {
              var parsedSortable = $column.sortable && $column.sortable();
              if (!parsedSortable) {
                  return;
              }
              var defaultSort = $scope.params.settings().defaultSort;
              var inverseSort = (defaultSort === 'asc' ? 'desc' : 'asc');
              var sorting = $scope.params.sorting() && $scope.params.sorting()[parsedSortable] && ($scope.params.sorting()[parsedSortable] === defaultSort);
              var sortingParams = (event.ctrlKey || event.metaKey) ? $scope.params.sorting() : {};
              sortingParams[parsedSortable] = (sorting ? inverseSort : defaultSort);
              $scope.params.parameters({
                  sorting: sortingParams
              });
          }
docs: /////////