code: def testProcNullPersistent(self):
      comm = self.COMM
      #
      req = comm.Send_init(None, MPI.PROC_NULL)
      req.Start()
      req.Wait()
      req.Free()
      #
      req = comm.Ssend_init(None, MPI.PROC_NULL)
      req.Start()
      req.Wait()
      req.Free()
      #
      buf = MPI.Alloc_mem(MPI.BSEND_OVERHEAD)
      MPI.Attach_buffer(buf)
      req = comm.Bsend_init(None, MPI.PROC_NULL)
      req.Start()
      req.Wait()
      req.Free()
      MPI.Detach_buffer()
      MPI.Free_mem(buf)
      #
      req = comm.Rsend_init(None, MPI.PROC_NULL)
      req.Start()
      req.Wait()
      req.Free()
      #
      req = comm.Recv_init(None, MPI.PROC_NULL)
      req.Start()
      req.Wait()
      req.Free()
  
imports: from mpi4py import MPI
  import mpiunittest
  import itertools
  import arrayimpl
label_desc: Use image node_id 8 for calling the BaseTestP2PBuf obj's underlying member method code with example usage: obj.testProcNullPersistent() without return types