protected function get_pre_scss_code() {
        $content = '';

        // Getting all the candidate functions.
        $candidates = array();
        foreach ($this->parent_configs as $parent_config) {
            if (!isset($parent_config->prescsscallback)) {
                continue;
            }
            $candidates[] = $parent_config->prescsscallback;
        }
        $candidates[] = $this->prescsscallback;

        // Calling the functions.
        foreach ($candidates as $function) {
            if (function_exists($function)) {
                $content .= "\n/** Pre-SCSS from $function **/\n" . $function($this) . "\n";
            }
        }

        return $content;
    }