'In the Cola backup mechanism, an object will not only be
put into a hash ring node, and also be put into the next
hash ring node which marked as a backup node. To the backup node,
it will remember the previous node\'s name.
:param addr: the node address to backup
:param pickled_objs: pickled objects
:param force: if True will be put into queue without checking duplication'

def put_backup_proxy(self, addr, pickled_objs, force=False):

    objs = pickle.loads(pickled_objs)
    self.put_backup(addr, objs, force=force)
