def METHOD_NAME(self):
    # roots
    self.assertEqual(self.p1.ancestors(with_self=False).count(), 0)
    self.assertEqual(self.p4.ancestors(with_self=False).count(), 0)
    self.assertEqual(self.p5.ancestors(with_self=False).count(), 0)
    # tree
    self.assertEqual(self.p5, self.p6.parent())