title: How to use simplejson to serialize and maintain properties?
body: <p>For a dictionary containing these two key-value pairs:</p>
  
  <pre><code>str = StringProperty
  time = DateTimeProperty
  </code></pre>
  
  <p>I want to serialize it to JSON, store it in the Datastore, and then fetch it, and deserialize it into the original properties.</p>