# File lib/flickr/upload.rb, line 35
        def to_s
                ([ "Content-Disposition: form-data" ] +
                attributes.map{|k,v| "#{k}=\"#{v}\""}).
                join('; ') + "\r\n"+
                (@mime_type ? "Content-Type: #{@mime_type}\r\n" : '')+
                "\r\n#{data}"
        end