code: def testIRecvAndSSend(self):
      comm = self.COMM
      rank = comm.Get_rank()
      for smess in messages:
          src = dst = rank
          req1 = comm.irecv(None, src, 1)
          req2 = comm.irecv(None, src, 2)
          req3 = comm.irecv(None, src, 3)
          comm.ssend(smess, dst, 3)
          comm.ssend(smess, dst, 2)
          comm.ssend(smess, dst, 1)
          self.assertEqual(smess, req3.wait())
          self.assertEqual(smess, req2.wait())
          self.assertEqual(smess, req1.wait())
          comm.ssend(smess, MPI.PROC_NULL, 3)
  
imports: from mpi4py import MPI
  import mpiunittest
  import threading
  import warnings
  import sys
label_desc: Use image node_id 12 for calling the BaseTestP2PObj obj's underlying member method code with example usage: obj.testIRecvAndSSend() without return types