public function init()
    {
        $json = [];
        foreach ($this->dataset as $file) {
            if (!(is_file($file) && is_readable($file))) {
                throw new Exception("File '$file' for dataset not readable.");
            }
            $content = file_get_contents($file);
            $key = pathinfo($file, PATHINFO_FILENAME);
            $json[$key] = json_decode($content, true);
        }

        $this->session->set(self::KEY, $json);
        return $this;
    }