code: def testIReadIWriteAtAll(self):
      comm = self.COMM
      size = comm.Get_size()
      rank = comm.Get_rank()
      fh = self.FILE
      for array, typecode in arrayimpl_loop_io():
          with arrayimpl.test(self):
              try:  # MPI 3.1
                  etype = array.TypeMap[typecode]
                  fh.Set_size(0)
                  fh.Set_view(0, etype)
                  count = 13
                  wbuf = array(42, typecode, count)
                  fh.Iwrite_at_all(count * rank, wbuf.as_raw()).Wait()
                  fh.Sync()
                  comm.Barrier()
                  fh.Sync()
                  rbuf = array(-1, typecode, count + 1)
                  fh.Iread_at_all(
                      count * rank, rbuf.as_mpi_c(count)
                  ).Wait()
                  for value in rbuf[:-1]:
                      self.assertEqual(value, scalar(42))
                  self.assertEqual(rbuf[-1], scalar(-1))
                  comm.Barrier()
              except NotImplementedError:
                  if MPI.Get_version() >= (3, 1):
                      raise
                  self.skipTest("mpi-iwrite_at_all")
  
imports: from mpi4py import MPI
  import mpiunittest
  import arrayimpl
  import os, tempfile
  import platform
label_desc: Use image node_id 8 for calling the BaseTestIOBasic obj's underlying member method code with example usage: obj.testIReadIWriteAtAll() without return types