code: def test_callback_thread(arg):
      def cb(x):
          return x + 1
  
      ret = dgl._api_internal._TestPythonCallbackThread(cb, arg)
      assert ret == arg + 1
  
file_path: dgl/tests/python/common/test_ffi.py
imports: import os
  import unittest
  import backend
  import dgl
  import numpy
  import pytest
label_desc: Use image node_id 4 for calling a global function with example usage: test_callback_thread(arg) and returns: unknown