docstr: Test most_similar returns correct results when `topn` is specified.
code: def test_most_similar_topn(self):
      """Test most_similar returns correct results when `topn` is specified."""
      self.assertEqual(
          len(self.vectors.most_similar("dog.n.01", topn=5)), 5
      )
      self.assertEqual(
          len(self.vectors.most_similar("dog.n.01", topn=10)), 10
      )
  
      predicted = self.vectors.most_similar("dog.n.01", topn=None)
      self.assertEqual(len(predicted), len(self.vectors) - 1)
      self.assertEqual(predicted[-1][0], "gallant_fox.n.01")
  
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 3 for calling the TestPoincareKeyedVectors obj's underlying member method code with example usage: obj.test_most_similar_topn() without return types