var instance = new GcSpread.Sheets.UndoRedo.RowGroupHeaderExpandUndoAction(sheet, rowGroupHeaderExpandExtent);
var value; // Type: boolean
value = instance.undo(arg);

function undo( 
   arg : object
) : boolean;

Parameters

arg

Data used by the action. If the action does not require data to be passed, this object can be set to null.

Return Value

Reference

RowGroupHeaderExpandUndoAction type