我了解以下代码检查插件是否已安装，如果未安装，则会在WP后端出错：

add_action(\'admin_notices\', \'showAdminMessages\');

function showAdminMessages()
{
    $plugin_messages = array();

include_once( ABSPATH . \'wp-admin/includes/plugin.php\' );

// Download the Yoast WordPress SEO plugin
if(!is_plugin_active( \'wordpress-seo/wp-seo.php\' ))
{
    $plugin_messages[] = \'This theme requires you to install the Yoast WordPress SEO plugin, <a href="http://wordpress.org/extend/plugins/wordpress-seo/">download it from here</a>.\';
}

// Download the Disqus comment system
if(!is_plugin_active( \'disqus-comment-system/disqus.php\' ))
{
    $plugin_messages[] = \'This theme requires you to install the Disqus comment system plugin, <a href="http://wordpress.org/extend/plugins/disqus-comment-system/">download it from here</a>.\';
}

if(count($plugin_messages) > 0)
{
    echo \'<div id="message" class="error">\';

        foreach($plugin_messages as $message)
        {
            echo \'<p><strong>\'.$message.\'</strong></p>\';
        }

    echo \'</div>\';
}

}

我的问题是：如何找到此行中使用的URL：

if(!is_plugin_active( \'disqus-comment-system/disqus.php\' ))

我正在尝试将此代码用于此代码段中未列出的其他插件，我不知道在哪里可以找到这些URL来检查插件是否被使用。任何帮助都将不胜感激。