code: def test_empty_flat(self):
      d = self.xq.shape[1] * 8
  
      index = faiss.IndexBinaryFlat(d)
  
      for use_heap in [True, False]:
          index.use_heap = use_heap
          Dflat, Iflat = index.search(self.xq, 10)
  
          assert np.all(Iflat == -1)
          assert np.all(Dflat == 2147483647)
  
imports: import os
  import numpy
  import unittest
  import faiss
  from common_faiss_tests import compare_binary_result_lists, make_binary_dataset
label_desc: Use image node_id 3 for calling the TestBinaryFlat obj's underlying member method code with example usage: obj.test_empty_flat() without return types