I Solved this ( I dont know if temporary solution)
Changed script name in /Framework/Runtime/Other/Hierarchy and named it as Hierarchy2
Then changed every mention of the old Hierarchy to Hierarchy2, this happened in the scripts GraphFinder.cs and Graph.cs
Im gonna atatch a zip with the changes. 🙂 I hope this could work for a future, and for someone lost.
There probably is another asset in your project that is using “Hierarchy” as a namespace.
Thanks for letting me know. I have renamed the class name to something different for the next version (which by the way has just been send to the Asset Store) 🙂