code: def post_comments(self, post_id, after='', order="chronological",
                        filter="stream", fields=None, **params):
  
          
          if fields:
              fields = ",".join(fields)
  
          parameters = {"access_token": self.key,
                        "after": after,
                        "order": order,
                        "fields": fields,
                        "filter": filter}
          parameters = self.merge_params(parameters, params)
  
          return self.api_call('%s/comments' % post_id, parameters)
docs: :param post_id:
          :param after:
          :param order: Can be 'ranked', 'chronological', 'reverse_chronological'
          :param filter: Can be 'stream', 'toplevel'
          :param fields: Can be 'id', 'application', 'attachment', 'can_comment',
          'can_remove', 'can_hide', 'can_like', 'can_reply_privately', 'comments',
          'comment_count', 'created_time', 'from', 'likes', 'like_count',
          'live_broadcast_timestamp', 'message', 'message_tags', 'object',
          'parent', 'private_reply_conversation', 'user_likes'
          :param params:
          :return: