class_docstr: Unit tests for the Prüfer sequence encoding and decoding
  functions.
class_docstr_tok: ["Unit","tests","for","the","Pr\u00fcfer","sequence","encoding","and","decoding","functions","."]
code: def test_trivial_graph(self):
      with pytest.raises(nx.NetworkXPointlessConcept):
          nx.to_prufer_sequence(nx.trivial_graph())
  
file_path: networkx/networkx/algorithms/tree/tests/test_coding.py
imports: from itertools import product
  import pytest
  import networkx
  from networkx.utils import edges_equal, nodes_equal
label_desc: Use image node_id 3 for calling the TestPruferSequence obj's underlying member method code with example usage: obj.test_trivial_graph() without return types