title: app engine ndb Key.get only returning the key?
body: <p>Given a Key that I construct, I would like to hit the datastore to see if it exists, but I want the cheapest (in time) way to do that. What I am looking for is like a keys only query but from get, e.g. my_key.get(keys_only=True). Does such an animal exist? It doesn't look like it to me. If not, is there some other way to achieve what I am after?</p>
  
  <p>Thanks.</p>