text: class Comment():
      def __init__(self, author, text, date, topic):
          self.author = author
          self.text = text
          self.date = date
          self.topic = topic
  
      def to_string(self):
          return 'author : ' + self.author + '\n' + \
              'text : ' + self.text + '\n' + \
              'date : ' + self.date + '\n' + \
              'topic : ' + self.topic
  