class_docstr: Unit tests for the bridge-finding function.
code: def test_barbell_graph(self):
      # The (3, 0) barbell graph has two triangles joined by a single edge.
      G = nx.barbell_graph(3, 0)
      source = 0
      bridges = list(nx.bridges(G, source))
      assert bridges == [(2, 3)]
  
file_path: networkx/networkx/algorithms/tests/test_bridges.py
imports: import pytest
  import networkx
label_desc: Use image node_id 2 for calling the TestBridges obj's underlying member method code with example usage: obj.test_barbell_graph() without return types