def +(row)
      rv = super(row)
      rv = Workbook::Row.new(rv) unless rv.class == Workbook::Row
      return rv
    end
def +(row)
      rv = super(row)
      rv = Workbook::Row.new(rv) unless rv.class == Workbook::Row
      return rv
    end
plus
 @param [Workbook::Row, Array] row to add
 @return [Workbook::Row] a new row, not linked to the table