code: def test_panther_similarity_isolated(self):
      G = nx.Graph()
      G.add_nodes_from(range(5))
      with pytest.raises(
          nx.NetworkXUnfeasible,
          match="Panther similarity is not defined for the isolated source node 1.",
      ):
          nx.panther_similarity(G, source=1)
  
imports: import pytest
  import networkx
  from networkx.algorithms.similarity import graph_edit_distance, optimal_edit_paths, optimize_graph_edit_distance
  from networkx.generators.classic import circular_ladder_graph, cycle_graph, path_graph, wheel_graph
label_desc: Use image node_id 42 for calling the TestSimilarity obj's underlying member method code with example usage: obj.test_panther_similarity_isolated() without return types