a memcached get() error .

[bai dongli]

We are running  memcached 1.4.4 with pylibmc0.9.2 wrapper package .
Recently , I have found some error messages on our web server ,the following
:

*A load persistent id instruction was encountered,
but no persistent_load function was specified.*
**

those error caused by get(k,v)  , the section of my python code following :

    def get(self, key, default=None):
        try:
            #print self._current.behaviors
            val = self._current.get(smart_str(key))
            print '-'*10,smart_str(key),type(key)
        except Exception,e:
            val = None
            *print '+'*10,smart_str(key),e,type(key)
*            #print >> sys.stderr,"get throw a exception !",e
        if val is None:
            return default
        else:
            if isinstance(val, basestring):
                return smart_unicode(val)
            else:
                return val

Anyone have a  good idea

thanks in advance !