title: deleting relationships in ndb entities (Google App Engine)
body: <p>I am implementing a Google App Engine based Web Application.
  The app uses ndb and there are two entities (say A and B) with a one to many relationship implemented via this property in the A class model</p>
  
  <pre><code> bObjects = ndb.KeyProperty(repeated=True);
  </code></pre>
  
  <p>I have an instance of A (a1) in relationship with three instance of B (b1,b2,b3)
  I am trying to delete b2.
  To this end I am trying to remove it from the relationship with a1 in this way</p>
  
  <pre><code>  a1.bObjects.remove(b2.key)
  </code></pre>
  
  <p>the command is executed but the element is not removed. What am I doing wrong?</p>