code: def test_ivf(self):
      index = faiss.index_factory(123, "IVF456,Flat")
      self.assertEqual(index.__class__, faiss.IndexIVFFlat)
  
imports: import numpy
  import unittest
  import gc
  import faiss
  from faiss.contrib import factory_tools
  from faiss.contrib import datasets
label_desc: Use image node_id 4 for calling the TestFactoryV2 obj's underlying member method code with example usage: obj.test_ivf() without return types