docstr: Edge flow betweenness centrality: C4
docstr_tok: ["Edge","flow","betweenness","centrality",":","C4"]
code: def test_C4(self):
      """Edge flow betweenness centrality: C4"""
      G = nx.cycle_graph(4)
      b = edge_current_flow(G, normalized=False)
      b_answer = {
          (0, 1): 1.25,
          (0, 3): 1.25,
          (1, 2): 1.25,
          (2, 3): 1.25,
      }
      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)
  
imports: import pytest
  import networkx
  from networkx import approximate_current_flow_betweenness_centrality
  from networkx import edge_current_flow_betweenness_centrality
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