code: def testSSendAndRecv(self):
      size = self.COMM.Get_size()
      rank = self.COMM.Get_rank()
      for smess in messages:
          self.COMM.ssend(smess, MPI.PROC_NULL)
          rmess = self.COMM.recv(None, MPI.PROC_NULL, 0)
          self.assertIsNone(rmess)
      if size == 1:
          return
      for smess in messages:
          if rank == 0:
              self.COMM.ssend(smess, rank + 1, 0)
              rmess = smess
          elif rank == size - 1:
              rmess = self.COMM.recv(None, rank - 1, 0)
          else:
              rmess = self.COMM.recv(None, rank - 1, 0)
              self.COMM.ssend(rmess, rank + 1, 0)
          self.assertEqual(rmess, smess)
  
imports: from mpi4py import MPI
  from mpi4py.util import pkl5
  import sys, os
label_desc: Use image node_id 5 for calling the BaseTest obj's underlying member method code with example usage: obj.testSSendAndRecv() without return types