public SheetResources sheetResources() {
        if (sheets.get() == null) {
            sheets.compareAndSet(null, new SheetResourcesImpl(this));
        }
        return sheets.get();
    }
public SheetResources sheetResources ( ) { if ( sheets . get ( ) == null ) { sheets . compareAndSet ( null , new SheetResourcesImpl ( this ) ) ; } return sheets . get ( ) ; }
Returns the SheetResources instance that provides access to Sheet resources.

@return the sheet resources