code: def test_tree_structure(self):
      # test for tree structure for nx.nonisomorphic_trees()
      def f(x):
          return list(nx.nonisomorphic_trees(x))
  
      for i in f(6):
          assert nx.is_tree(i)
      for i in f(8):
          assert nx.is_tree(i)
  
file_path: networkx/networkx/generators/tests/test_nonisomorphic_trees.py
imports: import networkx
  from networkx.utils import edges_equal
label_desc: Use image node_id 1 for calling the TestGeneratorNonIsomorphicTrees obj's underlying member method code with example usage: obj.test_tree_structure() and returns: list