def test_cyclic1(self): a = Dataset("a") b = Dataset("b") c = Dataset("c") d = Dataset("d") e = Dataset("e") f = Dataset("f") f.dependson(d, e) e.dependson(b, c) d.dependson(b) c.dependson(a, f) b.dependson(a) self.assertFalse(depgraph.is_acyclic(f))