code: def test_negcycle_infcap():
      G = nx.DiGraph()
      G.add_node("s", demand=-5)
      G.add_node("t", demand=5)
      G.add_edge("s", "a", weight=1, capacity=3)
      G.add_edge("a", "b", weight=3)
      G.add_edge("c", "a", weight=-6)
      G.add_edge("b", "d", weight=1)
      G.add_edge("d", "c", weight=-2)
      G.add_edge("d", "t", weight=1, capacity=3)
      pytest.raises(nx.NetworkXUnfeasible, nx.network_simplex, G)
  
imports: import bz2
  import importlib.resources
  import os
  import pickle
  import pytest
  import networkx
label_desc: Use image node_id 15 for calling a global function with example usage: test_negcycle_infcap() without return types