docstr: Edge betweenness subset centrality: box
docstr_tok: ["Edge","betweenness","subset","centrality",":","box"]
code: def test_box(self):
      """Edge betweenness subset centrality: box"""
      G = nx.Graph()
      G.add_edges_from([(0, 1), (0, 2), (1, 3), (2, 3)])
      b_answer = dict.fromkeys(G.edges(), 0)
      b_answer[(0, 1)] = b_answer[(0, 2)] = 0.25
      b_answer[(1, 3)] = b_answer[(2, 3)] = 0.25
      b = nx.edge_betweenness_centrality_subset(
          G, sources=[0], targets=[3], weight=None
      )
      for n in sorted(G.edges()):
          assert b[n] == pytest.approx(b_answer[n], abs=1e-7)
  
imports: import pytest
  import networkx
label_desc: Use image node_id 5 for calling the TestEdgeSubsetBetweennessCentrality obj's underlying member method code with example usage: obj.test_box() without return types