'A lease that has been released is removed from the Leases map.'

def test_lease_release(self):

    leases = self.leases.acquire(self.now, self.dataset_id, self.node_id)
    self.assertIn(self.dataset_id, leases)
    leases = leases.release(self.dataset_id, self.node_id)
    self.assertNotIn(self.dataset_id, leases)
