code: def testAccumulateProcNullSum(self):
      self.WIN.Fence()
      zeros = mkzeros(8)
      self.WIN.Fence()
      self.WIN.Accumulate(
          [zeros, MPI.INT], MPI.PROC_NULL, None, MPI.SUM
      )
      self.WIN.Fence()
      self.WIN.Accumulate([None, MPI.INT], MPI.PROC_NULL, None, MPI.SUM)
      self.WIN.Fence()
  
imports: from mpi4py import MPI
  import mpiunittest
  import contextlib
  import arrayimpl
  import sys
label_desc: Use image node_id 11 for calling the BaseTestRMA obj's underlying member method code with example usage: obj.testAccumulateProcNullSum() without return types