def to_csv
      CSV.generate do |csv|
        csv << fields
        authors.each do |author|
          csv << fields.map do |f|
            author.send(f)
          end
        end
      end
    end
def to_csv
      CSV.generate do |csv|
        csv << fields
        authors.each do |author|
          csv << fields.map do |f|
            author.send(f)
          end
        end
      end
    end
Generate csv output