class_docstr: Unit tests for the min_degree function
code: def test_not_sortable_nodes(self):
      G = nx.Graph([(0, "a")])
      treewidth_min_degree(G)
  
imports: import itertools
  import networkx
  from networkx.algorithms.approximation import treewidth_min_degree, treewidth_min_fill_in
  from networkx.algorithms.approximation.treewidth import MinDegreeHeuristic, min_fill_in_heuristic
label_desc: Use image node_id 7 for calling the TestTreewidthMinDegree obj's underlying member method code with example usage: obj.test_not_sortable_nodes() without return types