what's the difference between google.appengine.ext.ndb and gcloud.datastore? : <p>ndb: (from google.appengine.ext import ndb)</p>

<p>datastore: (from gcloud import datastore)</p>

<p>What's the difference? I've seen both of them used, and hints they both save data to google datastore. Why are there two different implementations?</p>
