def bottom_border_width=(width)
         size = width.nil? ? 0 : width
         if size > 0
            @borders[BOTTOM] = size.to_i
         else
            @borders[BOTTOM] = nil
         end
      end
def bottom_border_width=(width)
         size = width.nil? ? 0 : width
         if size > 0
            @borders[BOTTOM] = size.to_i
         else
            @borders[BOTTOM] = nil
         end
      end
This method assigns a border width to the bottom side of a table cell.
 Negative values are ignored and a value of 0 switches the border off.

 ==== Parameters
 width::  The new border width setting.