def set_primary_heartbeat(self, interface_id):
        """
        Set this interface as the primary heartbeat for this engine. 
        This will 'unset' the current primary heartbeat and move to
        specified interface_id.
        Clusters and Master NGFW Engines only.
        
        :param str,int interface_id: interface specified for primary mgmt
        :raises InterfaceNotFound: specified interface is not found
        :raises UpdateElementFailed: failed modifying interfaces
        :return: None
        """
        self.interface.set_unset(interface_id, 'primary_heartbeat')
        self._engine.update()