code: def test_dfs_edges(self):
      edges = nx.dfs_edges(self.G, source=0)
      assert list(edges) == [(0, 1), (1, 2), (2, 4), (1, 3)]
      edges = nx.dfs_edges(self.D)
      assert list(edges) == [(0, 1), (2, 3)]
  
imports: import networkx
label_desc: Use image node_id 7 for calling the TestDFS obj's underlying member method code with example usage: obj.test_dfs_edges() without return types