'Transfers the disk of a running instance in multiple phases, turning
off the instance before the end.
:param nova.objects.instance.Instance instance:
The instance whose disk should be migrated.
:param str dest:
The IP address of the destination host.
:param nova.objects.flavor.Flavor flavor:
The flavor of the instance whose disk get migrated.
:param nova.network.model.NetworkInfo network_info:
The network information of the given `instance`.
:param dict block_device_info:
Information about the block devices.
:param int timeout:
The time in seconds to wait for the guest OS to shutdown.
:param int retry_interval:
How often to signal guest while waiting for it to shutdown.
:return: A list of disk information dicts in JSON format.
:rtype: str'

def migrate_disk_and_power_off(self, context, instance, dest, flavor, network_info, block_device_info=None, timeout=0, retry_interval=0):

    raise NotImplementedError()
