code: function(cells, opt) {
  
          var preparedCells = joint.util.toArray(cells).map(function(cell) {
              return this._prepareCell(cell, opt);
          }, this);
          this.get('cells').reset(preparedCells, opt);
  
          return this;
      }
docs: When adding a lot of cells, it is much more efficient to reset the entire cells collection in one go. Useful for bulk operations and optimizations.