code: def test_negative_edge_cycle_empty(self):
      G = nx.DiGraph()
      assert not nx.negative_edge_cycle(G)
  
imports: import pytest
  import networkx
  from networkx.utils import pairwise
label_desc: Use image node_id 13 for calling the TestWeightedPath obj's underlying member method code with example usage: obj.test_negative_edge_cycle_empty() without return types