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()

def view_change_started(self, viewNo: int):
        """
        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()
        """
        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