def test_del_vertex(self):
g = Graph([v, w, x], [vw, vx, wx])
g.del_vertex(x)
assert g == Graph([v, w], [vw])
g.del_vertex(v)
assert g == Graph([w, ], [])
g.del_vertex(w)
assert g == Graph([], [])
def test_del_vertex_notthere(self):
g = Graph([v, w, x], [vw, vx, wx])
g.del_vertex(y)
assert g == Graph([v, w, x], [vw, vx, wx])