Retrieving an entity from GAE datastore by key

If I have the google assigned key of an entity in my datastore, say ag1iYXRjaC1nZW5lcmljchcLEgxCYXRjaGVzTW9kZWwiBUpvYiAyDA, is there a way I can easily fetch the entity by this key? I've tried using .get_by_id(), .filter('__key__=', 'ag1iYXRjaC1nZW5lcmljchcLEgxCYXRjaGVzTW9kZWwiBUpvYiAyDA') and can't seem to f开发者_StackOverflow社区ind anything that works. Any ideas?

db.get('ag1iYXRjaC1nZW5lcmljchcLEgxCYXRjaGVzTW9kZWwiBUpvYiAyDA')