code: def testGetSetErrhandler(self):
      eh = MPI.FILE_NULL.Get_errhandler()
      self.assertEqual(eh, MPI.ERRORS_RETURN)
      eh.Free()
      MPI.FILE_NULL.Set_errhandler(MPI.ERRORS_ARE_FATAL)
      eh = MPI.FILE_NULL.Get_errhandler()
      self.assertEqual(eh, MPI.ERRORS_ARE_FATAL)
      eh.Free()
      MPI.FILE_NULL.Set_errhandler(MPI.ERRORS_RETURN)
      eh = MPI.FILE_NULL.Get_errhandler()
      self.assertEqual(eh, MPI.ERRORS_RETURN)
      eh.Free()
  
imports: from mpi4py import MPI
  import mpiunittest
  import os, tempfile, pathlib
label_desc: Use image node_id 3 for calling the TestFileNull obj's underlying member method code with example usage: obj.testGetSetErrhandler() without return types