Native XML Plugin, export journal

Hi all!
I want write my plugin for OJS export journals for another scientometric databases.
And I want to understand how it works «Native XML Plugin».
At this stage, I’m trying to just export my log from the «XML Native Plugin» and get the following error:

Element '{}sections': Missing child element(s). Expected is ( {}section ).

Export full file:

If you need full file, I can upload in another services.

Help my please, how i can solved this problem? Tanks.
P.S. If you know article for create new plugins for OJS, leave them please. Thanks!

I solved my problem. Jusn need added article across submisions.