class_docstr: Intracommunicator class with scalable, point-to-point based
  implementations of global reduction operations.
code: def allreduce(self, sendobj=None, recvobj=None, op=MPI.SUM):
      recvobj = self.reduce(sendobj, recvobj, op, 0)
      recvobj = self.bcast(recvobj, 0)
      return recvobj
  
imports: from mpi4py import MPI
label_desc: Use image node_id 3 for calling the Intracomm obj's underlying member method code with example usage: obj.allreduce(sendobj, recvobj, op) and returns: recvobj