def table= t
      raise ArgumentError, "table should be a Workbook::Table (you passed a #{t.class})" unless t.is_a?(Workbook::Table) or t == nil
      if t
        @table = t
        table.push(self) #unless table.index(self) and self.placeholder?
      end
    end
def table= t
      raise ArgumentError, "table should be a Workbook::Table (you passed a #{t.class})" unless t.is_a?(Workbook::Table) or t == nil
      if t
        @table = t
        table.push(self) #unless table.index(self) and self.placeholder?
      end
    end
Set reference to the table this row belongs to and add the row to this table

 @param [Workbook::Table] t the table this row belongs to