code: def test_dsub2(self):
      self.do_test(16, 2)
  
imports: from __future__ import absolute_import, division, print_function
  import numpy
  import faiss
  import unittest
label_desc: Use image node_id 2 for calling the TestPQTransposedCentroids obj's underlying member method code with example usage: obj.test_dsub2() without return types