code: def receive_one(self):
          
          if self.nruns == 0:
              return None
          ret = self.communicationChannel.receive_one()
          if ret is not None:
              self.nruns -= 1
          return ret
docs: Return a pair of a run id and a result.
  
          This method waits until an event loop finishes.
          This method returns None if no loop is running.