public function theme($theme)
    {
        if ($this->isPlaylist() && $theme == static::THEME_DARK) {
            throw new AudioPlayerException('Playlists can not use the Dark Theme.  YouTube limitation.');
        }
        if ($theme != static::THEME_LIGHT && $theme != static::THEME_DARK) {
            throw new AudioPlayerException('Invalid Theme');
        }
        $this->theme = $theme;

        return $this;
    }