public static String getParentPlugin( Plugin plugin )
    {
        return getParentPlugin( XMPPServer.getInstance().getPluginManager().getPluginPath( plugin ) );
    }
Returns the name of the directory of the parent for this plugin. The value is retrieved from the plugin.xml file
of the plugin (which is casted down to lower-case). If the value could not be found, {@code null} will be returned.

@param plugin The plugin (cannot be null)
@return the parent plugin's directory name
xmppserver/src/main/java/org/jivesoftware/openfire/container/PluginMetadataHelper.java