'Enter into config_mode.'

def config_mode(self, config_command=u'', pattern=u''):

    output = u''
    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(u'Failed    to    enter    configuration    mode.')
    return output
