code: def test_threadsafety():
      def callback(a, caller):
          if a <= 0:
              return 1
          else:
              res = caller(lambda x: callback(x, caller), a - 1)
              return 2 * res
  
      def check(caller):
          caller = CALLERS[caller]
  
          results = []
  
          count = 10
  
          def run():
              time.sleep(0.01)
              r = caller(lambda x: callback(x, caller), count)
              results.append(r)
  
          threads = [threading.Thread(target=run) for j in range(20)]
          for thread in threads:
              thread.start()
          for thread in threads:
              thread.join()
  
          assert_equal(results, [2.0**count] * len(threads))
  
      for caller in CALLERS.keys():
          check(caller)
  
file_path: scipy/scipy/_lib/tests/test_ccallback.py
imports: from numpy.testing import assert_equal, assert_
  from pytest import raises
  import time
  import pytest
  import ctypes
  import threading
  from scipy._lib import _ccallback_c
  from scipy._lib import _test_ccallback
  from scipy._lib._ccallback import LowLevelCallable
label_desc: Use image node_id 8 for calling a global function with example usage: test_threadsafety() and returns: int, unknown