code: function(index) {
      if(lang.isNumber(index)&& this._elColgroup) {
          var nextSibling = this._elColgroup.childNodes[index] || null;
          this._elColgroup.insertBefore(document.createElement("col"), nextSibling);
      }
  }
docs: Adds a COL element to COLGROUP at given index.
  
  @method _insertColgroupColEl
  @param index {Number} Index of new COL element.
  @private