The python nodes API was manifested in T61655 and implemented in D4370 about a year ago.
There is still no any meaningful specification or documentation about the api and how to use it.
So it seems like the whole thing is pretty experimental and is not considered to provide much value to Blender.
In D6420 I’ve discovered over 30 (thirty) bugs in current implementation, having tested only refcounters of nodetrees and properties and calling of methods copy and free. My attempt of quick-n-dirty fix in D6484 only helps partially and introduces even more mess in code logic.
I would say, that the experiment is totally failed and the api should not be used in current state.
The question is if it’s even worth to (re)work on the api to make it usable, or it’s intended to be dropped anyway in favor of ‘everything nodes’ or something else.