code: def test_is_at_free():
      is_at_free = nx.asteroidal.is_at_free
  
      cycle = nx.cycle_graph(6)
      assert not is_at_free(cycle)
  
      path = nx.path_graph(6)
      assert is_at_free(path)
  
      small_graph = nx.complete_graph(2)
      assert is_at_free(small_graph)
  
      petersen = nx.petersen_graph()
      assert not is_at_free(petersen)
  
      clique = nx.complete_graph(6)
      assert is_at_free(clique)
  
      line_clique = nx.line_graph(clique)
      assert not is_at_free(line_clique)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_is_at_free() without return types