def _on_watermark_notification(self, notif):
<EOL>if self.get_user(notif.user_id).is_self:<EOL><INDENT>logger.info('<STR_LIT>'<EOL>.format(self.id_, notif.read_timestamp))<EOL>self_conversation_state = (<EOL>self._conversation.self_conversation_state<EOL>)<EOL>self_conversation_state.self_read_state.latest_read_timestamp = (<EOL>parsers.to_timestamp(notif.read_timestamp)<EOL>)<EOL><DEDENT>previous_timestamp = self._watermarks.get(<EOL>notif.user_id,<EOL>datetime.datetime.min.replace(tzinfo=datetime.timezone.utc)<EOL>)<EOL>if notif.read_timestamp > previous_timestamp:<EOL><INDENT>logger.info(('<STR_LIT>' +<EOL>'<STR_LIT>').format(self.id_,<EOL>notif.user_id.chat_id,<EOL>notif.read_timestamp))<EOL>self._watermarks[notif.user_id] = notif.read_timestamp<EOL><DEDENT>
Handle a watermark notification.