code: def test_undirected_graphs_are_not_supported():
      """
      Test that undirected graphs are not supported.
  
      d-separation and its related algorithms do not apply in
      the case of undirected graphs.
      """
      g = nx.path_graph(3, nx.Graph)
      with pytest.raises(nx.NetworkXNotImplemented):
          nx.is_d_separator(g, {0}, {1}, {2})
      with pytest.raises(nx.NetworkXNotImplemented):
          nx.is_minimal_d_separator(g, {0}, {1}, {2})
      with pytest.raises(nx.NetworkXNotImplemented):
          nx.find_minimal_d_separator(g, {0}, {1})
  
imports: from itertools import combinations
  import pytest
  import networkx
label_desc: Use image node_id 22 for calling a global function with example usage: test_undirected_graphs_are_not_supported() without return types