code: def mark_read(self, message=None):
          
          if message is None:
              if self._incoming:
                  message = self._incoming[-1].id
              else:
                  message = 0
          elif not isinstance(message, int):
              message = message.id
  
          return self._client.send_read_acknowledge(
              self._input_chat, max_id=message)
docs: Marks as read the latest received message if ``message is None``.
          Otherwise, marks as read until the given message (or message ID).
  
          This is equivalent to calling `client.send_read_acknowledge
          <telethon.client.messages.MessageMethods.send_read_acknowledge>`.