code: def test_on_disk():
      f = 2
      i = AnnoyIndex(f, "euclidean")
      i.on_disk_build("on_disk.ann")
      add_items(i)
      i.build(10)
      check_nns(i)
      i.unload()
      i.load("on_disk.ann")
      check_nns(i)
      j = AnnoyIndex(f, "euclidean")
      j.load("on_disk.ann")
      check_nns(j)
  
imports: import os
  import pytest
  from annoy import AnnoyIndex
label_desc: Use image node_id 4 for calling a global function with example usage: test_on_disk() without return types