'Retrieves id of the volume\'s backing LUN.
:param volume: volume information'

def get_lun_id(self, volume):

    if volume.provider_location:
        return utils.extract_provider_location(volume.provider_location, 'id')
    else:
        lun = self.client.get_lun(name=volume.name)
        return (lun.get_id() if (lun is not None) else None)
