Enter into config_mode.

        :param config_command: Configuration command to send to the device
        :type config_command: str

        :param pattern: Pattern to terminate reading of channel
        :type pattern: str

def config_mode(self, config_command="", pattern=""):
        """Enter into config_mode.

        :param config_command: Configuration command to send to the device
        :type config_command: str

        :param pattern: Pattern to terminate reading of channel
        :type pattern: str
        """
        output = ""
        if not self.check_config_mode():
            self.write_channel(self.normalize_cmd(config_command))
            output = self.read_until_pattern(pattern=pattern)
            if not self.check_config_mode():
                raise ValueError("Failed to enter configuration mode.")
        return output