code: def test_single_node(self):
      G1 = nx.Graph()
      G2 = nx.Graph()
      G1.add_node(1)
      G2.add_node(1)
  
      nx.set_node_attributes(
          G1, dict(zip(G1, it.cycle(labels_many))), "label"
      )
      nx.set_node_attributes(
          G2,
          dict(zip(G2, it.cycle(labels_many))),
          "label",
      )
      l1, l2 = (
          nx.get_node_attributes(G1, "label"),
          nx.get_node_attributes(G2, "label"),
      )
  
      gparams = _GraphParameters(
          G1,
          G2,
          l1,
          l2,
          nx.utils.groups(l1),
          nx.utils.groups(l2),
          nx.utils.groups(dict(G2.degree())),
      )
      m = _matching_order(gparams)
      assert m == [1]
  
imports: import itertools
  import pytest
  import networkx
  from networkx import vf2pp_is_isomorphic, vf2pp_isomorphism
  from networkx.algorithms.isomorphism.vf2pp import _consistent_PT, _cut_PT, _feasibility, _find_candidates, _find_candidates_Di, _GraphParameters, _initialize_parameters, _matching_order, _restore_Tinout, _restore_Tinout_Di, _StateParameters, _update_Tinout
label_desc: Use image node_id 2 for calling the TestNodeOrdering obj's underlying member method code with example usage: obj.test_single_node() without return types