code: def test_subgraph(self):
      G = self.G()
      G.add_edges_from(
          [("A", "B"), ("A", "C"), ("B", "D"), ("C", "B"), ("C", "D")]
      )
      SG = G.subgraph(["A", "B", "D"])
      assert nodes_equal(list(SG), ["A", "B", "D"])
      assert edges_equal(list(SG.edges()), [("A", "B"), ("B", "D")])
  
imports: import pytest
  import networkx
  from networkx import convert_node_labels_to_integers
  from networkx.utils import edges_equal, nodes_equal
label_desc: Use image node_id 26 for calling the HistoricalTests obj's underlying member method code with example usage: obj.test_subgraph() without return types