Post packing slip of sales order in X++

SalesFormletter SalesFormletter;
SalesTable SalesTable;
;

SalesFormletter = SalesFormletter::construct(DocumentStatus::Confirmation,true);

SalesTable.clear();
SalesTable = SalesTable::find(_salesId);
SalesFormletter.update(SalesTable, systemDateGet(), SalesUpdate::All, AccountOrder::None, false, false);