code: async def do_cmd(self, *args, success=None):
          
          if success is None:
              success = (250,)
  
          cmd = " ".join(args)
  
          await self.writer.send_command(cmd)
          code, message = await self.reader.read_reply()
  
          if code not in success:
              raise SMTPCommandFailedError(code, message, cmd)
  
          return code, message
docs: Sends the given command to the server.
  
          Args:
              *args: Command and arguments to be sent to the server.
  
          Raises:
              ConnectionResetError: If the connection with the server is
                  unexpectedely lost.
              SMTPCommandFailedError: If the command fails.
  
          Returns:
              (int, str): A (code, message) 2-tuple containing the server
                  response.