def modify_style_attribute( output_element, property, value )
      current = output_element.attribute("style")
      new_value = (current != nil) ? current.value + ";" : ""
      new_value += "#{property}:#{value}"
      output_element.attributes["style"] = new_value
    end
def modify_style_attribute( output_element, property, value )
      current = output_element.attribute("style")
      new_value = (current != nil) ? current.value + ";" : ""
      new_value += "#{property}:#{value}"
      output_element.attributes["style"] = new_value
    end
Modify the style attribute of <tt>output_element</tt> by adding
 the given <tt>property</tt> and <tt>value</tt>

 Algorithm:
   If there's no style attribute, create it.
   If it exists, look for the property.
     If the property doesn't exist, add it and its value
     If it does exist,