'Backup a server instance.
: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'

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

    return self.manager.backup(self, backup_name, backup_type, rotation)
