title: Do I need to explicitly use transactions with Django Rest Framework serializer updates?
body: <p>According to <a href="http://www.django-rest-framework.org/api-guide/serializers/#writable-nested-representations" rel="noreferrer">http://www.django-rest-framework.org/api-guide/serializers/#writable-nested-representations</a>, in order to accept a nested serializer I need to create an <code>update</code> method.  None of the examples use transactions although they do modify multiple rows/tables.  Does the DRF somehow wrap things in transactions already, or should I explicitly put <code>transaction.atomic()</code> all over it?</p>
  
  <p>Related PR:</p>
  
  <ul>
  <li><a href="https://github.com/tomchristie/django-rest-framework/pull/1787" rel="noreferrer">https://github.com/tomchristie/django-rest-framework/pull/1787</a></li>
  </ul>