*   <li>Supports a copy-free {@link #subArray} view, so methods that accept this type don't need to
 *       add overloads that accept start and end indexes.
 *   <li>Can be streamed without "breaking the chain": {@code foo.getBarInts().stream()...}.
 *   <li>Access to all collection-based utilities via {@link #asList} (though at the cost of
 *       allocating garbage).
 * </ul>
 *
 * <p>Disadvantages compared to {@code int[]}:
 *
 * <ul>

        assertEquals(2, a.getChildren().size());
        assertTrue(a.getChildren().contains(b));
        assertTrue(a.getChildren().contains(d));
        assertEquals(2, d.getParents().size());
        assertTrue(d.getParents().contains(a));
        assertTrue(d.getParents().contains(c));
    }

    @Test
    public void testCycleDetection() throws Exception {
        Graph graph1 = new Graph();
        addEdge(graph1, "a", "b");