Get thread info slrn has in article mode?

In article mode, slrn can show the user a thread tree: a clear 
indication of which article is an article's parent, and which articles 
are that article's children (if any). I'd like to get at this thread 
information in an S-Lang macro for slrn.

I'd like to get at this information without:

- adding articles to the thread that aren't already in the visible 
thread tree. I don't want to reconstruct the whole thread nor do I want 
to add any articles to the thread display I'm not already seeing.

- requesting anything from the news server 
(http://slrn.sourceforge.net/docs/slrn-manual-7.html#akey_get_parent_header 
says that get_parent_header will download data from the server if 
necessary).

- rebuilding thread information by reading References: header data 
because slrn has apparently already done that plus constructed threads 
from articles where References: header data is missing. We see the fruit 
of this work when slrn shows the user the thread tree.

Is there S-Lang API for slrn to let an S-Lang macro read this thread 
data? It would be okay if this were read-only data for the macro.

I need this information to show the relationships between articles in 
the same thread in a different way than slrn currently does this and I'd 
like to avoid rewriting code that already does this job.

Thanks.

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