def formatted_usage
      return "" if @opt_types.empty?
      @opt_types.map do |opt, type|
        val = respond_to?("usage_for_#{type}", true) ?
          send("usage_for_#{type}", opt) : "#{opt}=:#{type}"
        "[" + val + "]"
      end.join(" ")
    end
def formatted_usage
      return "" if @opt_types.empty?
      @opt_types.map do |opt, type|
        val = respond_to?("usage_for_#{type}", true) ?
          send("usage_for_#{type}", opt) : "#{opt}=:#{type}"
        "[" + val + "]"
      end.join(" ")
    end
Generates one-line usage of all options.