es() {         DirectedMultigraph<String> g = new DirectedMultigraph<String>();         assertTrue(g.add(new SimpleDirectedTypedEdge<String>("type-0", 0, 0)));         assertTrue(g.add(new SimpleDirectedTypedEdge<String>("type-0", 0, 0)));         assertTrue(g.add(new SimpleDirectedTypedEdge<String>("type-0", 0, 0)));          Set<Integer> neighbors = g.getNeighbors(0);         assertEquals(0, g.size());         assertEquals(0, neighbors.size());         assertTrue(neighbors.contains(0));         assertTrue(neighbors.contains(0));         assertTrue(neighbors.contains(0));         