def add(font)
         if font.instance_of?(Font)
            @fonts.push(font) if @fonts.index(font).nil?
         end
         self
      end
def add(font)
         if font.instance_of?(Font)
            @fonts.push(font) if @fonts.index(font).nil?
         end
         self
      end
This method adds a font to a FontTable instance. This method returns
 a reference to the FontTable object updated.

 ==== Parameters
 font::  A reference to the font to be added. If this is not a Font
         object or already exists in the table it will be ignored.