docs: def _req(self, req):
          """Send command and wait for response.
  
          The command will be repeated 3 times at most in case data loss of serial port.
  
          Args:
              req (str): Command to send, please do not include new line in the end.
  
          Returns:
              [str]: The output lines
          """
          logger.debug('DUT> %s', req)
          self._log and self.pause()
          times = 3
          res = None
  
          while times:
              times = times - 1
              try:
                  self._sendline(req)
                  self._expect(req)
  
                  line = None
                  res = []
  
                  while True:
                      line = self._readline()
                      logger.debug('Got line %s', line)
  
                      if line == 'Done':
                          break
  
                      if line:
                          res.append(line)
                  break
  
              except:
                  logger.exception('Failed to send command')
                  self.close()
                  self._init()
  
          self._log and self.resume()
          return res