code: def _hasViewChangeQuorum(self):
          # This method should just be present for master instance.
          
          num_of_ready_nodes = len(self._view_change_done)
          diff = self.quorum - num_of_ready_nodes
          if diff > 0:
              logger.info('{} needs {} ViewChangeDone messages'.format(self, diff))
              return False
  
          logger.info("{} got view change quorum ({} >= {})".
                      format(self.name, num_of_ready_nodes, self.quorum))
          return True
docs: Checks whether n-f nodes completed view change and whether one
          of them is the next primary