code: def testReductions(self):
      comm = self.COMM
      comm.Reduce(self.null_b, self.null_b)
      comm.Allreduce(self.null_b, self.null_b)
      comm.Reduce_scatter_block(self.null_b, self.null_b)
      rcnt = [0] * comm.Get_size()
      comm.Reduce_scatter(self.null_b, self.null_b, rcnt)
      try:
          comm.Scan(self.null_b, self.null_b)
      except NotImplementedError:
          pass
      try:
          comm.Exscan(self.null_b, self.null_b)
      except NotImplementedError:
          pass
  
file_path: mpi4py/test/test_msgzero.py
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 4 for calling the BaseTestMessageZero obj's underlying member method code with example usage: obj.testReductions() without return types