code: def test_multigraph_with_missing_attributes(self):
      G = nx.MultiGraph()
      G.add_node(0, label="1", color="green")
      G.add_node(1, label="2", color="green")
      G.add_edge(
          0, 1, id="0", weight=3, type="undirected", start=0, end=1
      )
      G.add_edge(0, 1, id="1", label="foo", start=0, end=1)
      G.add_edge(0, 1)
      fh = io.BytesIO()
      nx.write_gexf(G, fh)
      fh.seek(0)
      H = nx.read_gexf(fh, node_type=int)
      assert sorted(G.nodes()) == sorted(H.nodes())
      assert sorted(sorted(e) for e in G.edges()) == sorted(
          sorted(e) for e in H.edges()
      )
  
imports: import io
  import time
  import pytest
  import networkx
label_desc: Use image node_id 19 for calling the TestGEXF obj's underlying member method code with example usage: obj.test_multigraph_with_missing_attributes() without return types