to_s

# File lib/uri/mailto.rb, line 239
    def to_s
      @scheme + ':' +
        if @to
          @to
        else
          ''
        end +
        if @headers.size > 0
          '?' + @headers.collect{|x| x.join('=')}.join('&')
        else
          ''
        end +
        if @fragment
          '#' + @fragment
        else
          ''
        end
    end