code: function(value) {
              if (this._hasUndoLevel()) {
                  var c_html = this.getEditorHTML(), html;
                  if (!this._undoLevel) {
                      this._undoLevel = this._undoCache.length;
                  }
                  this._undoLevel = (this._undoLevel - 1);
                  if (this._undoCache[this._undoLevel]) {
                      html = this._getUndo(this._undoLevel);
                      if (html != c_html) {
                          this.setEditorHTML(html);
                      } else {
                          this._undoLevel = (this._undoLevel - 1);
                          html = this._getUndo(this._undoLevel);
                          if (html != c_html) {
                              this.setEditorHTML(html);
                          }
                      }
                  } else {
                      this._undoLevel = 0;
                      this.toolbar.disableButton('undo');
                  }
              }
              return [false];
          }
docs: /* {{{  Command Overrides - These commands are only over written when we are using the advanced version 
  @method cmd_undo
  @description Pulls an item from the Undo stack and updates the Editor
  @param value Value passed from the execCommand method