code: def test_multigraph_to_graph(self, tmp_path):
      # test converting multigraph to graph if no parallel edges found
      G = nx.MultiGraph()
      G.add_edges_from([("a", "b", 2), ("b", "c", 3)])  # no multiedges
      fname = tmp_path / "test.graphml"
      self.writer(G, fname)
      H = nx.read_graphml(fname)
      assert not H.is_multigraph()
      H = nx.read_graphml(fname, force_multigraph=True)
      assert H.is_multigraph()
  
      # add a multiedge
      G.add_edge("a", "b", "e-id")
      fname = tmp_path / "test.graphml"
      self.writer(G, fname)
      H = nx.read_graphml(fname)
      assert H.is_multigraph()
      H = nx.read_graphml(fname, force_multigraph=True)
      assert H.is_multigraph()
  
imports: import io
  import pytest
  import networkx
  from networkx.readwrite.graphml import GraphMLWriter
  from networkx.utils import edges_equal, nodes_equal
label_desc: Use image node_id 13 for calling the TestWriteGraphML obj's underlying member method code with example usage: obj.test_multigraph_to_graph(tmp_path) without return types