Support of non tree structures

[EdwardDiehl]

Hi! Thanks for the library!
Could someone tell, does the library work only with tree structures or it also supports non tree graphs like here?
https://en.wikipedia.org/wiki/Tree_(data_structure)#/media/File:Directed_graph_with_branching_SVG.svg
I mean structures with more than one root and multi parent nodes.

[jackc]

It only supports trees. It works with nodes that have a parent_id. So it can only support a single parent.