'Backup a server instance.
:param server: The :class:`Server` (or its ID) to share onto.
:param backup_name: Name of the backup image
:param backup_type: The backup type, like \'daily\' or \'weekly\'
:param rotation: Int parameter representing how many backups to
keep around.
:returns: An instance of novaclient.base.TupleWithMeta if the request
microversion is < 2.45, otherwise novaclient.base.DictWithMeta.'

def backup(self, server, backup_name, backup_type, rotation):

    body = {'name': backup_name, 'backup_type': backup_type, 'rotation': rotation}
    return self._action('createBackup', server, body)
