def transform_comments(separator, &block)
      if @comments.empty?
        nil
      else
        block ||= lambda { |c| c }
        @comments.map(&block).join(separator)
      end
    end
def transform_comments(separator, &block)
      if @comments.empty?
        nil
      else
        block ||= lambda { |c| c }
        @comments.map(&block).join(separator)
      end
    end
Transform the list of comments as specified by the block and
 join with the separator.