async def config_mode(self):
    'Enter to configuration mode'
    logger.info('Host {}: Entering to configuration mode'.format(self._host))
    output = ''
    config_enter = type(self)._config_enter
    if (not (await self.check_config_mode())):
        self._stdin.write(self._normalize_cmd(config_enter))
        output += (await self._read_until_prompt())
        if (not (await self.check_config_mode())):
            raise ValueError('Failed to enter to configuration mode')
    return output
Enter to configuration mode
async def config_mode(self):
    
    logger.info('Host {}: Entering to configuration mode'.format(self._host))
    output = 
    config_enter = type(self)._config_enter
    if (not (await self.check_config_mode())):
        self._stdin.write(self._normalize_cmd(config_enter))
        output += (await self._read_until_prompt())
        if (not (await self.check_config_mode())):
            raise ValueError('Failed to enter to configuration mode')
    return output