docstr: Betweenness Centrality Subset: box
docstr_tok: ["Betweenness","Centrality","Subset",":","box"]
code: def test_box(self):
      """Betweenness Centrality Subset: box"""
      G = nx.Graph()
      G.add_edges_from([(0, 1), (0, 2), (1, 3), (2, 3)])
      b_answer = {0: 0, 1: 0.25, 2: 0.25, 3: 0}
      b = nx.betweenness_centrality_subset(
          G, sources=[0], targets=[3], weight=None
      )
      for n in sorted(G):
          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 TestSubsetBetweennessCentrality obj's underlying member method code with example usage: obj.test_box() without return types