code: def test_christofides_incomplete_graph():
      G = nx.complete_graph(10)
      G.remove_edge(0, 1)
      pytest.raises(nx.NetworkXError, nx_app.christofides, G)
  
imports: import random
  import pytest
  import networkx
  import networkx.algorithms.approximation
label_desc: Use image node_id 2 for calling a global function with example usage: test_christofides_incomplete_graph() without return types