code: def test_factory_fast_scan(self):
      index = faiss.index_factory(56, "PQ28x4fs")
      self.assertEqual(index.bbs, 32)
      self.assertEqual(index.pq.nbits, 4)
      index = faiss.index_factory(56, "PQ28x4fs_64")
      self.assertEqual(index.bbs, 64)
      index = faiss.index_factory(
          56, "IVF50,PQ28x4fs_64", faiss.METRIC_INNER_PRODUCT
      )
      self.assertEqual(index.bbs, 64)
      self.assertEqual(index.nlist, 50)
      self.assertTrue(index.cp.spherical)
      index = faiss.index_factory(56, "IVF50,PQ28x4fsr_64")
      self.assertTrue(index.by_residual)
      index = faiss.index_factory(56, "PQ28x4fs,RFlat")
      self.assertEqual(index.k_factor, 1.0)
  
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 9 for calling the TestFactory obj's underlying member method code with example usage: obj.test_factory_fast_scan() without return types