code: def test_simple_scalar_cache(tmpdir):
      """Testing trivial NullCache: should trigger value generating function on each run"""
      cache = LocalDiskCache(tmpdir.strpath, 1 * MB, 4)
      assert 42 == cache.get("some_key", lambda: 42)
      assert 42 == cache.get("some_key", lambda: 43)
  
imports: import os
  import numpy
  from petastorm.local_disk_cache import LocalDiskCache
label_desc: Use image node_id 2 for calling a global function with example usage: test_simple_scalar_cache(tmpdir) without return types