def testUnionNeighbors(self):
g = DalGraph(make_claw())
result = g.union_neighbors([0])
expect = [1, 2, 3]
self.assertEqual(result, expect)
g._g.add_node(4)
g._g.add_edge(3, 4)
result =g.union_neighbors([4, 2])
expect = [3, 0]
self.assertEqual(result, expect)
