title: How to add extra fields to a django model by extending it?
body: <p>I am developing a django application using Pinax Stripe(<a href="https://github.com/pinax/pinax-stripe" rel="nofollow">https://github.com/pinax/pinax-stripe</a>). Pinax stripe is a bundled application which has a model called 'Plans'. Now in my application, I want to add some extra fields to the model 'Plans' in my application BUT without modifying the original pinax stripe application.</p>
  
  <p>Something like this:</p>
  
  <pre><code>    #models.py
  from pinax-stripe.models import Plan
  
  class UserProfile(models.Model):
      #write the extra fields here
  </code></pre>
  
  <p>Is there any way I can do it and then register it with admin so i can add data to those fields in admin panel?</p>