'Store some leases in the persistence service.
:return: ``Deferred`` that fires when done.'

def save_leases(self):

    self.clock.advance(self.now)
    leases = Leases().acquire(datetime.fromtimestamp(self.now, tz=UTC), self.dataset1, self.node1, self.expires)
    leases = leases.acquire(datetime.fromtimestamp(self.now, tz=UTC), self.dataset2, self.node2, None)
    self.time_passed = 3
    self.clock.advance(self.time_passed)
    return self.persistence_service.save(Deployment(leases=leases))
