code: def view_change_started(self, viewNo: int):
          
          if viewNo <= self.viewNo:
              logger.warning("{}Provided view no {} is not greater"
                             " than the current view no {}"
                             .format(VIEW_CHANGE_PREFIX, viewNo, self.viewNo))
              return False
          self.previous_master_primary = self.node.master_primary_name
          for replica in self.replicas.values():
              replica.primaryName = None
          return True
docs: Notifies primary decider about the fact that view changed to let it
          prepare for election, which then will be started from outside by
          calling decidePrimaries()