code: def testGatherIntra(self):
      comm = self.COMM
      size = comm.Get_size()
      rank = comm.Get_rank()
      for smess in messages:
          for root in range(size):
              rmess = comm.gather(smess, root)
              if rank == root:
                  self.assertEqual(rmess, [smess] * size)
              else:
                  self.assertIsNone(rmess)
      self.assertRaises(MPI.Exception, comm.gather, None, root=-1)
      self.assertRaises(MPI.Exception, comm.gather, None, root=size)
  
imports: from mpi4py import MPI
  from mpi4py.util import pkl5
  import sys, os
label_desc: Use image node_id 26 for calling the BaseTest obj's underlying member method code with example usage: obj.testGatherIntra() without return types