code: def test_prefault():
      i = AnnoyIndex(10, "angular")
      i.load("test/test.tree", prefault=True)
      assert i.get_nns_by_item(0, 10) == [
          0,
          85,
          42,
          11,
          54,
          38,
          53,
          66,
          19,
          31,
      ]
  
imports: import os
  import random
  import pytest
  from annoy import AnnoyIndex
label_desc: Use image node_id 15 for calling a global function with example usage: test_prefault() without return types