code: def testDefault(self):
      pickle = self.pickle
      protocols = [0, 1, 2, 3, 4]
      if sys.version_info[:2] >= (3, 8):
          protocols.append(5)
      protocols.append(-1)
      protocols.append(None)
      for proto in protocols:
          pickle.__init__(protocol=proto)
          for obj in OBJS:
              self.do_pickle(obj, pickle)
          self.do_pickle(OBJS, pickle)
  
file_path: mpi4py/test/test_pickle.py
imports: from mpi4py import MPI
  import mpiunittest
  import sys
label_desc: Use image node_id 4 for calling the TestPickle obj's underlying member method code with example usage: obj.testDefault() without return types