code: def test_infinite_capacity_neg_digon():
      """An infinite capacity negative cost digon results in an unbounded
      instance."""
      nodes = [(1, {}), (2, {"demand": -4}), (3, {"demand": 4})]
      edges = [
          (1, 2, {"weight": -600}),
          (2, 1, {"weight": 0}),
          (2, 3, {"capacity": 5, "weight": 714285}),
          (3, 2, {"capacity": 2, "weight": 0}),
      ]
      G = nx.DiGraph(edges)
      G.add_nodes_from(nodes)
      pytest.raises(nx.NetworkXUnbounded, nx.network_simplex, G)
  
imports: import bz2
  import importlib.resources
  import os
  import pickle
  import pytest
  import networkx
label_desc: Use image node_id 21 for calling a global function with example usage: test_infinite_capacity_neg_digon() without return types