code: def test_negative_weight_bf_path(self):
      G = nx.DiGraph()
      G.add_nodes_from("abcd")
      G.add_edge("a", "d", weight=0)
      G.add_edge("a", "b", weight=1)
      G.add_edge("b", "c", weight=-3)
      G.add_edge("c", "d", weight=1)
  
      assert nx.bellman_ford_path(G, "a", "d") == ["a", "b", "c", "d"]
      assert nx.bellman_ford_path_length(G, "a", "d") == -1
  
imports: import pytest
  import networkx
  from networkx.utils import pairwise
label_desc: Use image node_id 17 for calling the TestBellmanFordAndGoldbergRadzik obj's underlying member method code with example usage: obj.test_negative_weight_bf_path() without return types