docstr: Edge betweenness subset centrality: P1
  if n <= 1: no normalization b=0 for all nodes
docstr_tok: ["Edge","betweenness","subset","centrality",":","P1","if","n","<","=","1",":","no","normalization","b=0","for","all","nodes"]
code: def test_normalized_p1(self):
      """
      Edge betweenness subset centrality: P1
      if n <= 1: no normalization b=0 for all nodes
      """
      G = nx.Graph()
      nx.add_path(G, range(1))
      b_answer = dict.fromkeys(G.edges(), 0)
      b = nx.edge_betweenness_centrality_subset(
          G, sources=[0], targets=[0], normalized=True, weight=None
      )
      for n in G.edges():
          assert b[n] == pytest.approx(b_answer[n], abs=1e-7)
  
imports: import pytest
  import networkx
label_desc: Use image node_id 9 for calling the TestEdgeSubsetBetweennessCentrality obj's underlying member method code with example usage: obj.test_normalized_p1() without return types