code: def test_round_trip_empty_graph(self):
      G = nx.Graph()
      A = nx.nx_agraph.to_agraph(G)
      H = nx.nx_agraph.from_agraph(A)
      # assert graphs_equal(G, H)
      AA = nx.nx_agraph.to_agraph(H)
      HH = nx.nx_agraph.from_agraph(AA)
      assert graphs_equal(H, HH)
      G.graph["graph"] = {}
      G.graph["node"] = {}
      G.graph["edge"] = {}
      assert graphs_equal(G, HH)
  
imports: import warnings
  import pytest
  import networkx
  from networkx.utils import edges_equal, graphs_equal, nodes_equal
label_desc: Use image node_id 19 for calling the TestAGraph obj's underlying member method code with example usage: obj.test_round_trip_empty_graph() without return types