docstr: Betweenness centrality: Ladder graph
docstr_tok: ["Betweenness","centrality",":","Ladder","graph"]
code: def test_ladder_graph(self):
      """Betweenness centrality: Ladder graph"""
      G = nx.Graph()  # ladder_graph(3)
      G.add_edges_from(
          [(0, 1), (0, 2), (1, 3), (2, 3), (2, 4), (4, 5), (3, 5)]
      )
      b_answer = {
          0: 1.667,
          1: 1.667,
          2: 6.667,
          3: 6.667,
          4: 1.667,
          5: 1.667,
      }
      for b in b_answer:
          b_answer[b] /= 2
      b = nx.betweenness_centrality(G, weight=None, normalized=False)
      for n in sorted(G):
          assert b[n] == pytest.approx(b_answer[n], abs=1e-3)
  
imports: import pytest
  import networkx
label_desc: Use image node_id 11 for calling the TestBetweennessCentrality obj's underlying member method code with example usage: obj.test_ladder_graph() without return types