title: ValueError: Key() must have an even number of positional arguments. Python App Engine NDB
body: <p>ValueError: Key() must have an even number of positional arguments.</p>
  
  <p>When I try:</p>
  
  <pre><code>class MyStorage(ndb.Model):
   my_attr = ndb.StringProperty()
  
   my = MyStorage(parent=ndb.Key('mylist'), key_name='myattr', my_attr = 'hello')
  </code></pre>
  
  <p>What am I doing wrong? </p>
  
  <p>My aim is to store a few MyStorage entities under a parent entity with key 'mylist'. I don't want to attach anything to the parent itself, and neither have I instantiated it, but from the docs I didn't get the impression that was necessary.</p>
  
  <p>How do I persist MyStorage entities the way I describe above correctly?</p>