def test_out_vertices(self):
g = Graph([v, w, x], [vw, vx])
assert sorted(g.out_vertices(v)) == sorted([w, x])
assert g.out_vertices(w) == [v, ]
assert g.out_vertices(x) == [v, ]
def test_out_vertices_none(self):
g = Graph()
assert [] == g.out_vertices(v)
