code: def test_single_node_graph(self):
      G = nx.DiGraph()
      G.add_node(0)
      assert nx.single_source_bellman_ford_path(G, 0) == {0: [0]}
      assert nx.single_source_bellman_ford_path_length(G, 0) == {0: 0}
      assert nx.single_source_bellman_ford(G, 0) == ({0: 0}, {0: [0]})
      assert nx.bellman_ford_predecessor_and_distance(G, 0) == (
          {0: []},
          {0: 0},
      )
      assert nx.goldberg_radzik(G, 0) == ({0: None}, {0: 0})
  
imports: import pytest
  import networkx
  from networkx.utils import pairwise
label_desc: Use image node_id 1 for calling the TestBellmanFordAndGoldbergRadzik obj's underlying member method code with example usage: obj.test_single_node_graph() without return types