docstr: Edge betweenness centrality: C4
docstr_tok: ["Edge","betweenness","centrality",":","C4"]
code: def test_C4(self):
      """Edge betweenness centrality: C4"""
      G = nx.cycle_graph(4)
      b = edge_current_flow_subset(G, list(G), list(G), normalized=True)
      b_answer = edge_current_flow(G, normalized=True)
      for (s, t), v1 in b_answer.items():
          v2 = b.get((s, t), b.get((t, s)))
          assert v1 == pytest.approx(v2, abs=1e-7)
  
file_path: networkx/networkx/algorithms/centrality/tests/test_current_flow_betweenness_centrality_subset.py
imports: import pytest
  import networkx
  from networkx import edge_current_flow_betweenness_centrality
  from networkx import edge_current_flow_betweenness_centrality_subset
label_desc: Use image node_id 3 for calling the TestEdgeFlowBetweennessCentrality obj's underlying member method code with example usage: obj.test_C4() without return types