code: def test_custom_node_attr_dict_safekeeping(self):
      class custom_dict(dict):
          pass
  
      class Custom(nx.Graph):
          node_attr_dict_factory = custom_dict
  
      g = nx.Graph()
      g.add_node(1, weight=1)
  
      h = Custom(g)
      assert isinstance(g._node[1], dict)
      assert isinstance(h._node[1], custom_dict)
  
imports: import pytest
  import networkx
  from networkx.convert import from_dict_of_dicts, from_dict_of_lists, to_dict_of_dicts, to_dict_of_lists, to_networkx_graph
  from networkx.generators.classic import barbell_graph, cycle_graph
  from networkx.utils import edges_equal, graphs_equal, nodes_equal
label_desc: Use image node_id 11 for calling the TestConvert obj's underlying member method code with example usage: obj.test_custom_node_attr_dict_safekeeping() without return types