[Python] networkx: identify instances where a node is both an ancestor and descendant of...

I'm not sure if specific terminology exists for this, but I'm looking to identify paths in a directed network in which case the directionality goes both ways. I'm building a network with a bunch of provided data and by accident stumbled on some artifacts where nodes A and B are both parents/children of each other.

In looking to identify these, I stumbled on the term "self loop". This is what I want, just for paths longer than a single edge.

import networkx as nx
g = nx.DiGraph()
g.add_edges_from([(0, 1), (0, 2), (0, 3), (1, 3), (3, 0), (3, 3), (2, 0), (1, 2), (2, 1)])
nx.draw_networkx(g, arrows=True, with_labels=True, width=0.2, edge_color='#AAAAAA', arrowsize=20,
node_size=2)




networkx has a function to identify nodes with self loops, but I only get node 3 as a result.

list(nx.nodes_with_selfloops(g))
[3]


Only node 3 is identified, but in this case I'd be looking to identify that 1/2 and 0/1 have arrows going both ways. It's not a single edge self loop, but allows 2 > 0 > 1 > 2 and 1 > 3 > 0 > 2 > 1. I start and end at the same node, just with other nodes between.

Is there an efficient way to identify "what nodes that have bi-directional arrows to the same node"? I have not identified enough of these cases to know if the cause will always be a single double sided arrow or something like 2+ multi-edge paths that start/stop with the same node.

The real world data is like process flows, so there should not be cases where somehow A flows to B and B also flows into A, so these are the data inconsistencies I'm looking to quickly identify.

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