docstr: Test ancestors returns expected list and returns empty list for highest node in hierarchy.
code: def test_ancestors(self):
      """Test ancestors returns expected list and returns empty list for highest node in hierarchy."""
      expected = [
          "canine.n.02",
          "carnivore.n.01",
          "placental.n.01",
          "mammal.n.01",
      ]
      self.assertEqual(self.vectors.ancestors("dog.n.01"), expected)
      expected = []
      self.assertEqual(self.vectors.ancestors("mammal.n.01"), expected)
  
imports: import logging
  import os
  import tempfile
  import unittest
  import numpy
  from gensim.models.poincare import PoincareRelations, PoincareModel, PoincareKeyedVectors
  from gensim.test.utils import datapath
label_desc: Use image node_id 15 for calling the TestPoincareKeyedVectors obj's underlying member method code with example usage: obj.test_ancestors() without return types