let mut graph1 = petgraph::graph::DiGraph::<(), u8>::new();
let g10 = graph1.add_node(());
let g11 = graph1.add_node(());

graph1.add_edge(g10, g11, 0);
graph1.add_edge(g10, g11, 1);

let mut graph2 = petgraph::graph::DiGraph::<(), u8>::new();
let g20 = graph2.add_node(());
let g21 = graph2.add_node(());
let g22 = graph2.add_node(());
let g23 = graph2.add_node(());
graph2.add_edge(g20, g22, 0);
graph2.add_edge(g20, g21, 1);
graph2.add_edge(g21, g23, 0);
graph2.add_edge(g21, g22, 1);
graph2.add_edge(g22, g23, 1);

assert!(!petgraph::algo::is_isomorphic_subgraph_matching(&&graph1, &&graph2, &mut <()>::eq, &mut u8::eq));