code: def test_is_minimal_d_separator_checks_dsep():
      """Test that is_minimal_d_separator checks for d-separation as well."""
      g = nx.DiGraph()
      g.add_edges_from(
          [
              ("A", "B"),
              ("A", "E"),
              ("B", "C"),
              ("B", "D"),
              ("D", "C"),
              ("D", "F"),
              ("E", "D"),
              ("E", "F"),
          ]
      )
  
      assert not nx.is_d_separator(g, {"C"}, {"F"}, {"D"})
  
      # since {'D'} and {} are not d-separators, we return false
      assert not nx.is_minimal_d_separator(g, "C", "F", {"D"})
      assert not nx.is_minimal_d_separator(g, "C", "F", set())
  
imports: from itertools import combinations
  import pytest
  import networkx
label_desc: Use image node_id 27 for calling a global function with example usage: test_is_minimal_d_separator_checks_dsep() without return types