'Get the next device name based on the block device mapping.
:param instance: nova.objects.instance.Instance that volume is
requesting a device name
:param bdms: a nova.objects.BlockDeviceMappingList for the instance
:param block_device_obj: A nova.objects.BlockDeviceMapping instance
with all info about the requested block
device. device_name does not need to be set,
and should be decided by the driver
implementation if not set.
:returns: The chosen device name.'

def get_device_name_for_instance(self, instance, bdms, block_device_obj):

    raise NotImplementedError()
