Nutch parise和index Open Graph metatag

Question

我正在使用Nutch 1.10和Solr 6.4，并且有一个问题需要解析/索引Open Graph元标记，比如

<meta property="og:description" content="xyz.">.

following nutch-site.xml config works for metatag.description,metatag.keywords,metatag.twitter:description, but it's failed for metatag.og:description. 
Appreciate any helps.


    <property>
        <name>metatags.names</name>
        <value>*</value>
        <description></description>
    </property>
    <property>
        <name>metatags.property</name>
        <value>*</value>
        <description></description>
    </property>
    <property>
        <name>index.parse.md</name>
        <value>metatag.description,metatag.keywords,metatag.twitter:description,metatag.og:description</value>
        <description></description>
    </property>