# File lib/aws/s3/prefixed_collection.rb, line 61
      def with_prefix prefix, mode = :replace
        new_prefix = case mode
        when :replace then prefix
        when :append  then "#{@prefix}#{prefix}"
        when :prepend then "#{prefix}#{@prefix}"
        else
          raise ArgumentError, "invalid prefix mode `#{mode}`, it must be " +
            ":replace, :append or :prepend"
        end
        self.class.new(bucket,
                       :prefix => new_prefix)
      end