code: def test_IndexPreTransform_2(self):
      sub_index = faiss.IndexFlatL2(d)
      index = faiss.IndexPreTransform(sub_index)
      ltrans = faiss.NormalizationTransform(d)
      index.prepend_transform(ltrans)
      index.add(xb)
      del ltrans
      gc.collect()
      index.add(xb)
      del sub_index
      gc.collect()
      index.add(xb)
  
file_path: faiss/tests/test_referenced_objects.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import numpy
  import unittest
  import faiss
  import sys
  import gc
label_desc: Use image node_id 5 for calling the TestReferenced obj's underlying member method code with example usage: obj.test_IndexPreTransform_2() without return types