code: function(cells, opt) {
  
          return joint.util.toArray(cells).reduce(function(memo, cell) {
              if (cell.isLink()) return memo;
              var rect = cell.getBBox(opt);
              var angle = cell.angle();
              if (angle) rect = rect.bbox(angle);
              if (memo) {
                  return memo.union(rect);
              } else {
                  return rect;
              }
          }, null);
      }
docs: Return the bounding box of all cells in array provided. Links are being ignored.