code: def testCollectivesVector(self):
      comm = self.COMM
      comm.Gatherv(self.null_b, self.null_v)
      comm.Scatterv(self.null_v, self.null_b)
      comm.Allgatherv(self.null_b, self.null_v)
      comm.Alltoallv(self.null_v, self.null_v)
  
file_path: mpi4py/test/test_msgzero.py
imports: from mpi4py import MPI
  import mpiunittest
label_desc: Use image node_id 3 for calling the BaseTestMessageZero obj's underlying member method code with example usage: obj.testCollectivesVector() without return types