title: django can we select related a field on a prefetch related model?
body: <p>Assuming these as django model for the sake of simplcity:</p>
  
  <pre><code>class A():
  
      a = manytomany('B')
  
  class B():
  
      b = charfield()
      z = foreignkey('C')
  
  class C():
  
      c = charfield()
  </code></pre>
  
  <p>Can we do something like this to fetch the <code>z</code> also:</p>
  
  <pre><code>foo = A.objects.get(pk = 1).prefetch_related('a').select_related('a__z')
  </code></pre>