code: def tearDown(self):
      MPI.FILE_NULL.Set_errhandler(self.eh_save)
      self.eh_save.Free()
  
imports: from mpi4py import MPI
  import mpiunittest
  import os, tempfile, pathlib
label_desc: Use image node_id 2 for calling the TestFileNull obj's underlying member method code with example usage: obj.tearDown() without return types