code: def test_serialization(self):
      import faiss
  
      index = FaissIndex(metric_type=faiss.METRIC_INNER_PRODUCT)
      index.add_vectors(np.eye(5, dtype=np.float32))
  
      # Setting delete=False and unlinking manually is not pretty... but it is required on Windows to
      # ensure somewhat stable behaviour. If we don't, we get PermissionErrors. This is an age-old issue.
      # see https://bugs.python.org/issue14243 and
      # https://stackoverflow.com/questions/23212435/permission-denied-to-write-to-my-temporary-file/23212515
      with tempfile.NamedTemporaryFile(delete=False) as tmp_file:
          index.save(tmp_file.name)
          index = FaissIndex.load(tmp_file.name)
      os.unlink(tmp_file.name)
  
      query = np.zeros(5, dtype=np.float32)
      query[1] = 1
      scores, indices = index.search(query)
      self.assertGreater(scores[0], 0)
      self.assertEqual(indices[0], 1)
  
imports: import os
  import tempfile
  from functools import partial
  from unittest import TestCase
  from unittest.mock import patch
  import numpy
  import pytest
  from datasets.arrow_dataset import Dataset
  from datasets.search import ElasticSearchIndex, FaissIndex, MissingIndex
  from .utils import require_elasticsearch, require_faiss
label_desc: Use image node_id 4 for calling the FaissIndexTest obj's underlying member method code with example usage: obj.test_serialization() without return types