Test if string is valid key prior to memcache.get()
Any object is a valid key, provided that the object can be serialized using pickle.  If pickle.dumps(key) succeeds, then you shouldn't get a BadKeyError.
Is there a function in Google App Engine to test if a string is valid 'string key' prior to calling memcache.get(key) without using db.get() or db.get_by_key_name() first?
In my case the key is being passed from the user's get request: 
obj = memcache.get(self.request.get("obj"))
Somehow I'd like to know if that string is a valid key string without calling the db first, which would defeat the purpose of using memcache.