code: def test_PQ6x8(self):
      self.do_encode_twice("PQ6np")
  
imports: from __future__ import print_function
  import numpy
  import unittest
  import faiss
  from common_faiss_tests import get_dataset_2
  from faiss.contrib.datasets import SyntheticDataset
  from faiss.contrib.inspect_tools import get_additive_quantizer_codebooks
label_desc: Use image node_id 5 for calling the TestEncodeDecode obj's underlying member method code with example usage: obj.test_PQ6x8() without return types