# File lib/optparse.rb, line 631
    def summarize(*args, &block)
      list.each do |opt|
        if opt.respond_to?(:summarize) # perhaps OptionParser::Switch
          opt.summarize(*args, &block)
        elsif !opt
          yield("")
        elsif opt.respond_to?(:each_line)
          opt.each_line(&block)
        else
          opt.each(&block)
        end
      end
    end