def del_lease(mac, ip_address):
 api = network_rpcapi.NetworkAPI()
 api.release_fixed_ip(context.get_admin_context(), ip_address, CONF.host, mac)

def del_lease ( mac , ip_address ) : api = network_rpcapi . NetworkAPI ( ) api . release_fixed_ip ( context . get_admin_context ( ) , ip_address , CONF . host , mac )
called when a lease expires .