private function lineBreak()
    {
        if ($this->previousRoot !== $this->directive &&
            in_array($this->directive, array_keys(RobotsTxtParser::TOP_LEVEL_DIRECTIVES)) ||
            $this->previous !== self::DIRECTIVE_USER_AGENT &&
            $this->directive === self::DIRECTIVE_USER_AGENT
        ) {
            $this->previousRoot = $this->directive;
            if ($this->level >= 1) {
                return $this->eol;
            }
        }
        return '';
    }